Daytime Ion Research Articles

Diurnal Variations and Source Apportionment of Water-soluble Ions in PM2.5During Winter in Nanjing Jiangbei New Area

To gain a better understanding of the day-night variation characteristics of water-soluble ions, PM2.5 samples were continuously collected for two months in the Nanjing Jiangbei New Area during winter. The diurnal variation and sources of water-soluble ions were studied. Results showed that the mass concentration of water-soluble ions ranged from 17.07 μg·m-3 to 168.43 μg·m-3 with a mean value of (59.01±30.75) μg·m-3. The average mass concentration of water-soluble ions in daytime was higher than that in the nighttime. The concentration ratio of NO3- and NH4+ to total ion concentrations was higher at night, while SO42- and Cl- were higher during daytime. SO42-, NO3-, and NH4+ (SNA) were the dominant species of water-soluble ions in PM2.5 in Nanjing. The mass concentration of SNA on polluted days was higher than that on clean days. The ratio of the anion-cation balance (AE/CE) was larger than 1, indicating that the PM2.5 was acidic. There was a significant linear correlation between NH4+ with NO3- and SO42-, indicating that it occurred mainly in the form of NH4NO3 and (NH4)2SO4 in PM2.5. The PMF source apportionment indicated that water-soluble ions of PM2.5 were mainly derived from motor vehicle emissions, fossil fuel combustion, biomass burning, and dust in the Nanjing Jiangbei New Area.

Universal time variation of high‐latitude thermospheric disturbance wind in response to a substorm

AbstractThe temporal and spatial variation in thermospheric winds are studied at 400 km altitude in response to substorms that start at different universal time (UT), using a global ionosphere and thermosphere model. The substorm‐induced disturbance winds at high latitudes are mainly in the poleward, westward, and upward directions in the dusk sector and in the equatorward, westward, and upward directions in the nighttime. The daytime perturbation is due to ion drag, driven by variations in interplanetary magnetic field Bz, whereas the nighttime perturbation is due to both the Bz and hemispheric power input. The nightside disturbed winds respond somewhat later than the dayside owing to low background ion density. Ion drag is the dominant driving force in the daytime for both meridional and zonal disturbed winds, whereas Joule heating is the dominant factor for the vertical winds. The nighttime meridional and zonal winds are driven by a combination of ion drag, Joule heating, and heating of the auroral belt, whereas the vertical winds are mainly caused by auroral belt heating. The viscous force acts to resist the ion drag, whereas the Coriolis force is negligible. The disturbed winds exhibit large variations with UT during equinox and local winter conditions. With more solar illumination, stronger disturbed winds can be generated. Weak or even opposite variations with UT in the disturbed winds are found in local summer, which is due to a smaller UT variation of the daytime ion density and a larger contribution from auroral heating than from ion drag.

Stable sulfur isotope ratios and water-soluble inorganic compositions of PM10 in Yichang City, central China.

Chemical and sulfate-sulfur isotopic compositions of water-soluble inorganic ions were analyzed for aerosol sample particulate matter with aerodynamic diameter ≤10μm (PM10) collected during 17-28 December 2012 at Yichang City, Hubei Province, central China. Most water-soluble inorganic ions, except for NO3 (-) and NH4 (+), showed slightly higher concentration in daytime than in nighttime, and the major detected ions followed the order of SO4 (2-) > NO3 (-) > Ca(2+) > Na(+) > NH4 (+) > Cl(-) in daytime and nighttime, of which SO4 (2-) is the most abundant ionic component that accounted for about 49.1 and 49.3% of the total mass of analyzed ions in daytime and nighttime, respectively. According to the correlation coefficients among the mass concentrations of water-soluble inorganic ions, there may mainly exist in forms of (NH4)2SO4 and NH4NO3 in daytime and NH4NO3 in nighttime. The δ(34)S values of sulfate ranged from +2.82 to +4.63 ‰ (average +3.97 ‰) in daytime and from +2.90 to +5.39 ‰ (average +4.08 ‰) in nighttime, indicating that the source of sulfate in PM10 was mainly derived from coal burning (δ(34)S, +3.68 ‰) in Yichang City. The [NO3 (-)]/[SO4 (2-)] mass ratio varied between 0.2 and 0.6 with an average of 0.4 in daytime and 0.1 to 0.8 with an average of 0.4 in nighttime, which implying that the stationary source emissions would be more important than the vehicle emissions in the studied area. As a whole, the mixture of coal burning, vehicle exhaust, and resuspended road dust would be responsible for the sources of PM10 in Yichang City during wintertime.

Effect of solar cycle on topside ion temperature measured by SROSS C2 and ROCSAT 1 over the Indian equatorial and low latitudes

Abstract. The effect of solar activity on the diurnal, seasonal and latitudinal variations of ion temperature Ti and its relationship with corresponding ion density Ni over the Indian low and equatorial topside ionosphere within 17.5° S to 22.5° N magnetic latitudes are being investigated, combining the data from SROSS C2 and ROCSAT 1 for the 9-year period from 1995 to 2003 during solar cycle 23. Ti varies between 800 K and 1100 K during nighttime and rises to peak values of ~1800 K in the post sunrise hours. Daytime Ti varies from 1000 K to 1500 K. The time of occurrence, magnitude and duration of the morning enhancement show distinct seasonal bias. For example, in the June solstice, Ti increases to ~1650 K at ~06:00 h and exhibits a daytime plateau till 17:00 LT. In the equinoxes, enhanced ion temperature is observed for a longer duration in the morning. There is also a latitudinal asymmetry in the ion temperature distribution. In the equinoxes, the daytime Ti is higher at off equatorial latitudes and lower over the Equator, while in the solstices, Ti exhibits a north–south gradient during daytime. Nighttime Ti is found to be higher over the Equator. Daytime ion temperature exhibits insignificant positive correlation with F10.7 cm solar flux, while nighttime ion temperature decreases with increase in solar flux. Daytime ion temperature and ion density are negatively correlated during solar minimum, while nighttime Ti does not exhibit any correlation. However, during high solar activity, significant positive correlation of Ti with Ni has been observed over the Equator, while at 10° S and 10° N temperature and density exhibit significant negative correlation. The neutral temperature Tn derived from the MSISE 90 model is found to be higher than measured Ti during nighttime, while daytime Ti is higher than model Tn.

Ionospheric and thermospheric variations associated with prompt penetration electric fields

This paper presents a comprehensive modeling investigation of ionospheric and thermospheric variations during a prompt penetration electric field (PPEF) event that took place on 9 November 2004, using the Thermosphere‐Ionosphere‐Mesosphere Electrodynamic General Circulation Model (TIMEGCM). The simulation results reveal complex latitudinal and longitudinal/local‐time variations in vertical ion drift in the middle‐ and low‐latitude regions owing to the competing influences of electric fields and neutral winds. It is found that electric fields are the dominant driver of vertical ion drift at the magnetic equator; at midlatitudes, however, vertical ion drift driven by disturbance meridional winds exceeds that driven by electric fields. The temporal evolution of the UT‐latitude electron density profile from the simulation depicts clearly a super‐fountain effect caused by the PPEF, including the initial slow‐rise of the equatorial F‐layer peak height, the split of the F‐layer peak density, and the subsequent downward diffusion of the density peaks along magnetic field lines. Correspondingly, low‐latitude total electron content (TEC) becomes bifurcated around the magnetic equator. The O/N2column density ratio, on the other hand, shows very little variations during this PPEF event, excluding composition change as a potential mechanism for the TEC variations. By using realistic, time‐dependent, high‐latitude electric potential and auroral precipitation patterns to drive the TIMEGCM, the model is able to successfully reproduce the large vertical ion drift of ∼120 m/s over the Jicamarca incoherent radar (IS) in Peru, which is the largest daytime ion drift ever recorded by the radar. The simulation results are validated with several key observations from IS radars, ground GPS‐TEC network, and the TIMED‐GUVI O/N2column density ratio. The model‐data intercomparison also reveals some deficiencies in the TIMEGCM, particularly the limitations imposed by its upper boundary height as well as the prescribed O+ flux.

Model calculations of the silicon and magnesium chemistry in the mesosphere and lower thermosphere

Steady state solutions of the diffusion and continuity equations for silicon and magnesium species are presented to investigate the characteristics of the height distribution of the different constituents. We account for deposition of the metals, diffusion and kinetics, including the most recent laboratory data of reaction constants. It is commonly accepted that the major source in the mesosphere of metals is meteoric ablation, which implies that both Si and Mg compounds are dominant next to Fe relative to other metals on the basis of their relative abundance in chondritic meteorites. However, recent models and measurements indicate a depletion for some metals (Ca, Fe, Mg) relative to sodium as a result of an incomplete evaporation of certain minerals in metoroids. The depletion of Si, Fe and Mg relative to Na in the lower thermosphere is determined by comparing modelled column densities to two in situ rocket measurements of metallic ions in daytime.

Ionosphere‐protonosphere thermal plasma fluxes estimated from Magion 2 and ionosonde data in August–September 1990

The daytime thermal plasma fluxes at the topside of the midlatitude ionosphere were assessed during a quiet period and a recovery phase of a magnetic storm in summer 1990. Using in situ measurements of electron concentration and temperature and a crude estimate of mean ion mass performed by the Magion 2 subsatellite in an altitudinal range from 1200 to 2500 km, in addition to data supplied by ground‐based ionosondes, electron concentration profiles were drawn by means of a theoretical one‐dimensional steady state ionospheric model. Latitudinal variations of daytime ion fluxes at the 1000‐km‐height level during quiet periods revealed a peak at L = 2.5 ÷ 3.0 with maximum values up to 7 × 108 cm−2 s−1. The difference in flux versus latitude behavior between quiet and poststorm periods was clearly observable for L > 3. The uncertainty in the resultant ion fluxes depends upon the accuracy of the electron temperature and ƒoF2 measurements, as well as on the neutral wind velocity approximation, and was estimated to be about 50 percent. A comparison of the ion flows obtained with either direct measurements or indirect estimations made earlier show reasonable agreement.

Comparison between the IRI ion composition and incoherent scatter measurement and theoretical values

Comparisons have been made between the percentage of light ions in the upper ionosphere as predicted by the IRI model and as found in incoherent scatter (ICS) measurements at the stations Millstone Hill, Arecibo and Jicamarca. Major discrepancies are observed in both day and night. The IRI values are always considerably larger than the ICS measurements. Theoretical values are calculated as well, assuming chemical equilibrium and using the MSIS neutral density model /1/. In most cases these theoretical values favour the ICS values; only for the daytime ion composition above Millstone Hill has better agreement with the IRI model been found.

Stratospheric positive ion composition measurements, ion abundances and related trace gas detection

Positive ion spectra obtained from measurements with a balloon-borne mass spectrometer during three balloon flights are critically investigated and compared with other data. Ion abundances for proton hydrates [H +(H 2O) n ions] at different stratospheric temperatures are compared, as well as the abundances of non proton hydrates H +X itl(H 2O) m , X being most likely CH 3CN. The detection of trace gases from ion composition measurements is discussed and an upper limit for the number densities of minor constituents such as NH 3 and CH 3OH is estimated at 35 km. Although sodium compounds cannot be responsible for the major positive ions, a closer investigation of high resolution daytime spectra suggests a small contribution of sodium in daytime ion chemistry.

Ion drifts observed at Malvern: evidence of ion drag and substorm induced electric fields

Day-time ion drift observations, made at Malvern (52.1°N, 2.3°W) using an incoherent scatter radar in quadristatic configuration during the period October 1972 to October 1974 are analysed. Out of the seventeen days' observations considered here nine are magnetically quiet days and eight are magnetically disturbed days. A significant negative correlation was observed between v ∥ (field aligned ion drift) and v TN (crossfield drift in meridional plane) on all the days, indicating that ion drag is important even on magnetically disturbed days. Drifts along the field line v ∥ ' ( v ∥ after removing the ion drag component) showed less day-to-day variability as compared to v ⊥ N and v ⊥ E where v ⊥ E is the crossfield drift in the zonal plane. The value of v ∥ 'is ~20 ms −1 and it is found to be mostly downwards. Crossfield drifts ( v ⊥ N , v ⊥ E ) showed larger day-to-day variability indicating the same variability for their driving electric fields. Values of v ⊥ E are found to be larger than those of v ⊥ N indicating stronger north-south electric fields. The large day-to-day variability in crossfield drifts suggest that even on quiet days there is a significant contribution from electric fields of magnetospheric origin. A major substorm event on 18 September 1974 is accompanied by a substantial reduction in eastward drift ( v ⊥ e ) though change in v ⊥ N is comparatively smaller. Similar changes are noticed for other substorm events occurring in after noon hours in European longitude zone. These results confirm that substorm electric fields penetrate down to the latitude of Malvern.

Daytime nitric oxide at the base of the thermosphere

Nitric oxide profiles are deduced from the analysis of 10 daytime ion composition experiments performed at various latitudes, seasons, and solar conditions, principally over an altitude region from 85 to 100 km. Within a factor of 3, nitric oxide concentrations are found to vary from 1 × 108 cm−3 at 100 km to 2×106 cm−3 at 85 km for various sunspot numbers and seasons, except winter. This strong gradient suggests a vertical eddy diffusion coefficient on the lower side of those thought to be appropriate. The three winter mid‐latitude data sets, all associated with anomalous D region radio absorption, yield higher NO concentrations, two profiles attaining peak values of 109 cm−3.

Comparison of measured and calculated thermospheric molecular oxygen densities

The open source neutral mass spectrometers on the AE-C, -D, and -E satellites were equipped with a 'fly-through' mode of operation which has provided direct measurements of molecular oxygen densities over a large portion of the globe. A complementary set of O2 densities is derived by using AE ion measurements and a scheme based on the daytime ion chemistry of O2(+) in the thermosphere. A comparison of the two data sets reveals general agreement over northern latitudes during periods of relatively low Ap and F10.7. The simplifying assumptions made in the photochemical scheme require that caution be used in calculating O2, especially at high latitudes and altitudes below 200 km

Mesostheric temperatures and the formation of water cluster ions in the D region

The roles of three-body attachments to CO 2 and N 2, and subsequent switching reactions with water vapour, in the successive hydration of NO + ions are examined. Use is made of recent laboratory measurements relating to the temperature dependence of the three-body attachment rate of NO + to N 2. It is found that for temperatures representative of mesospheric conditions the formation of water cluster ions from NO + ions in daytime can be explained quantitatively on the basis of these attachment and switching reactions. Furthermore, it is shown that variations of rate coefficients arising out of seasonal changes in mesospheric temperatures will contribute to seasonal differences in D-region ion composition.

Molecular oxygen abundances in the thermosphere from Atmosphere Explorer-C ion composition measurements

We present a scheme for the daytime ion chemistry of O2+ in the thermosphere and use it to derive molecular oxygen abundances from ion composition measurements on board the Atmosphere Explorer-C satellite. The molecular oxygen abundance varies from about 1.0 × 108 to 5.0 × 108 cm−3 at 200 km. No seasonal variation is found, but a significant increase in mean O2 density occurs at high geomagnetic latitudes. We also find a small variation of the O2 density with local time.

Daytime ion composition in the height range of 150–1500 km for solar minimum condition

An ion composition model for the height range 150–1500 km, likely to hold for day-time at moderate latitudes for minimum solar activity ( F 10.7 = 70 units † † 1 unit = 10 −22 W/m 2/cps of 10.7 cm solar radiation. ) has been developed. It is based on the neutral atmospheric model given by Bhatnagar and Mitra (1966), solar ionizing flux data given by Hinteregger et al. (1965) and the electron and ion temperatures given by evans (1965) close to minimum solar activity period. The topside ionosphere has been considered as a ternary mixture of atomic oxygen, helium and atomic hydrogen ions. The calculated distribution of O + agrees with that observed in the bottomside F2-region, if the rate coefficients k 1 and k 2 for the charge exchange between O + and N 2, and O + and O 2 have values of about (0.9–1.0) × 10 −12 cm 3/s and (0.9–1.0) × 10 −11 cm 3/s respectively, at F-region temperatures. These values agree within a factor of 2 with measured laboratory values. In the case of helium ions a reasonable agreement between the calculated and observed values is obtained, if the rate coefficients k 3 and k 4 for the charge exchange between He + and N 2, and He + and O 2 have values of about 10 −11 cm 3/sec. In the ease of atomic hydrogen ions, agreement between the calculated and observed values is obtained, if the neutral atomic hydrogen distribution from the atmospheric model is increased by a factor of about 5–10. It is concluded that the electron and ion temperatures in the topside ionosphere above about 500 km, obtained from incoherent scatter technique are larger than those required to explain the observed ionic composition at dip values around 60° for low solar activity conditions.

Ion temperature and relative ion composition measurements from a low-altitude polar-orbiting satellite

An ion energy analyzer has been flown on a recent (November 9-11, 1965) low-altitude polar-orbiting satellite. The data were collected, partially analyzed while in flight by the instrument, and stored on tape to be read out at convenient satellite tracking stations. The data sampling rate was once every three seconds, which permitted a very detailed measure of the latitude variation of ion temperature, concentration, and relative ion composition. Large temperature fluctuations were observed in the nighttime northern high-latitude regions. Mid-latitude daytime ion temperatures generally varied between 400 and 1000°K. High temperatures were observed in both the daytime southern auroral zone and the nighttime northern auroral zone. The midlatitude trough in ion concentration was observed a L = 4.5, while other sharp troughs were located at about L = 1.5.

Direct measurements bearing on the extent of thermal nonequilibrium in the ionosphere

Two ejectable instrument packages, consisting of a spherical ion trap and a cylindrical electrostatic probe, were flown above Eglin Air Force Base, Florida. The first was launched near midday local time on August 3, 1962, and the second was launched at mid-night October 24, 1962. The experimental technique is briefly reviewed. The major steps in the derivation of the equations for the ion current to a moving spherical ion trap are given, and the assumptions used in obtaining these equations are discussed. The daytime ion temperature profile derived directly from the ion. trap displays isothermal characteristics from 180 km up to 365 km, the apogee of the flight. This directly measured value of 1500°K compares reasonably well with the ion temperature value of 1650°K derived from the scale height of measured ion density. Electron temperature obtained from both the cylindrical probe and the ion trap showed a monotonie increase with altitude. The electron temperature measured at the apogee of the flight, 2750°K, indicates a high degree of thermal nonequilibrium. There is extremely good agreement between the electron temperature profiles obtained by the two methods. The nighttime electron temperature results also showed excellent agreement. The midnight electron temperature was 1000°K and isothermal from 150 km to 488 km, the apogee of the flight. No direct ion temperature information was obtained from the night flight; however, when we used the ion density results, the scale-height method indicated that the electrons and ions were essentially in thermal equilibrium. The results from these flights are compared with the results of other experiments and, from the daytime data, it is noted that the effects of an ionospheric storm on the electron temperature last longer than present-day theories would predict. The nighttime results indicate that a particle flux may play an important role in the heating of the ionosphere at night.