摘要:

A steady state solution for the self‐consistent electrostatic potential due to a plasma confined in a magnetic flux tube is considered. A steady state distribution function is constructed for the trapped particles from the constants of the motion, in the absence of waves and collisions. Using Liouville's theorem, the particle density along the geomagnetic field is determined and found to depend on the local magnetic field, self‐consistent electric potential, and the equatorial plasma distribution function. A hot anisotropic magnetospheric plasma in steady state is modeled by a bi‐Maxwellian at the equator. The self‐consistent electric potential along the magnetic field is calculated assuming quasineutrality, and the potential drop is found to be approximately equal to the average kinetic energy of the equatorially trapped plasma. The potential is compared with that obtained by Alfvén and Fälthamm

ISSN:0094-8276    

DOI:10.1029/93GL01251

年代:1993

数据来源: WILEY

摘要:

Solar EUV observations from the Langmuir probe on Pioneer Venus Orbiter suggest that at EUV wavelengths solar cycle 22 was more active than solar cycle 21. The Langmuir probe, acting as a photodiode, measured the integrated solar EUV flux over a 13 1/2 year period from January 1979 to June 1992, the longest continuous solar EUV measurement. The Ipe EUV flux correlated very well with the SME measurement of Lαduring the lifetime of SME and with the UARS SOLSTICE Lαfrom October 1991 to June 1992 when the Ipe measurement ceased. Starting with the peak of solar cycle 21, there was good general agreement of Ipe EUV with the 10.7 cm, Ca K, and He 10830 solar indices, until the onset of solar cycle 22. From 1989 to the start of 1992, the 10.7 cm flux exhibited a broad maximum consisting of two peaks of nearly equal magnitude, whereas Ipe EUV exhibited a strong increase during this time period making the second peak significantly higher than the first. The only solar index that exhibits the same increase in solar activity as Ipe EUV and Lαduring the cycle 22 peak is the total magnetic flux. The case for high activity during this peak is also supported by the presence of very high solar flare intensi

ISSN:0094-8276    

DOI:10.1029/93GL01453

年代:1993

数据来源: WILEY

摘要:

The nightside ionosphere of Mars could be produced by electron precipitation or by plasma transport from the dayside, by analogy to the Venus, but few measurements are available. We report here model calculations of upper limits to the nightside ion densities on Mars that would be produced by both mechanisms. For the auroral model, we have adopted the downward traveling portions of the electron spectra measured by the HARP instrument on the Soviet Phobos spacecraft in the Martian plasma sheet and in the magnetotail lobes. For the plasma transport case, we have imposed on a model of the nightside thermosphere, downward fluxes of O+, C+, N+, NO+and O+2that are near the maximum upward fluxes that can be sustained by the dayside ionosphere. The computed electron density peaks are in the range (1.3–1.9) × 104cm−3at altitudes of 159 to 179 km. The major ion for all the models is O+2, but significant differences in the composition of the minor ions are found for the ionospheres produced by auroral precipitation and by plasma transport. The calculations reported here provide a guide to the data that should be acquired during a future aeronomy mission to Mars, in order to determine the sources of the nightside ionosp

ISSN:0094-8276    

DOI:10.1029/93GL01349

年代:1993

数据来源: WILEY

摘要:

The interaction of the thermosphere and ionosphere is largely governed by collisions between ions and neutral particles. On Venus and the Earth, O+is a dominant ion, and atomic O dominates throughout much of the thermosphere; therefore an accurate O+‐O cross section is an important prerequisite for understanding the dynamics of planetary upper atmospheres. The cross section and momentum, transfer collision frequency are calculated with a quantum mechanical code which includes resonance charge exchange, polarization, and charge‐quadrupole effects. Our results agree well with earlier calculations of Stubbe [1968] and Stallcopet al[19

ISSN:0094-8276    

DOI:10.1029/93GL01597

年代:1993

数据来源: WILEY

摘要:

On May 31, 1992, a rocket payload equipped with 10 airglow photometers was launched from the Alcântara Launch Center in Northern Brazil. The payload was designed to measure sodium, hydroxyl, atomic and molecular oxygen airglow emissions, in addition to electron density and temperature. At the time of launch, a sodium lidar was operated at the same site, giving vertical profiles of atmospheric sodium density. The measured vertical profiles of the Na D line emission and atomic sodium density are remarkably similar, with sharp boundaries at 81 km and 99 km. On the assumption that the Chapman mechanism is responsible for the Na D emission, the measurements imply an almost constant ozone density of 4×107cm−3between 87 and 99 km. The unexpectedness of this height independent ozone concentration suggests that our understanding of the sodium excitation mechanism might be inadequ

ISSN:0094-8276    

DOI:10.1029/93GL01121

年代:1993

数据来源: WILEY

摘要:

The last two winter‐spring seasons (DJFM) distinguished themselves by being with the lowest ever total ozone over all three continental size regions between 45°N and 65°N of North America, Europe and Siberia. The total ozone deficiencies for the entire season over all of the above mentioned regions were about 11% and 13% below the long‐term normal during the two consecutive years (1991/92 and 1992/93 respectively ). This helped to pull down the cumulative ozone decline since the winter‐spring of 1969/70 to be about 14% in the latitude belt of the 45°N–65°N. Frequencies of days with ozone values deviating below the long‐term mean by more than 2σ have been ten times higher than their 35‐year average. There are evidences deduced from trajectories on potential temperature surfaces that transport of poor in ozone air masses forced in addition by vertical motions, could account for a number of the extreme cases. There is also evidence that cold air, known to have excess ClO content, has moved over the sun lighted latitudes on many occasions, when chemical ozone destruction could have been favored. These ozone deficiencies do not have similar rates of decline and did not reach even close to the extreme low values regularly observed during the Antarctic‐spring oz

ISSN:0094-8276    

DOI:10.1029/93GL01309

年代:1993

数据来源: WILEY

摘要:

A telescope‐attached FT‐IR spectral radiometer was applied for remote measurement of chemical composition of the volcanic gas of Unzen volcano, Japan, which started erupting in November 1990. The observations were carried out at the site about 1.3 km away from the gas‐emitting region of the volcano in March and July 1992. Absorption features of SO2(Vl) and HCl were identified and column amounts of SO2and HCl of the volcanic gas plume were estimated using a nonlinear least‐squares method. The SO2/HCl ratio was in the range between 0.7 and 1.8 for both March and July observations. This is the first remote ground‐based observation of HCl in vol

ISSN:0094-8276    

DOI:10.1029/93GL01065

年代:1993

数据来源: WILEY

摘要:

Rate constants for the reactions of OH with HFC‐134a (CF3CH2F) have been measured relative to CH3CCl3, CH4and HFC‐125 (CF3CHF2). Rate constants for HFC‐134 (CF2HCF2H) were measured relative to CH3CCl3, HFC‐125, and HFC‐134a. The measurements were made in a slow‐flow, temperature controlled photochemical reactor, and were based on relative rates of disappearance of the parent compounds as measured by FTIR spectroscopy. The temperature range was 298–358 K. Hydroxyl radicals were generated by 254 nm photolysis of O3in the presence of water vapor. Using current NASA/JPL rate constants for the reference compounds, temperature dependent rate constants of both compounds were derived. Rate constants obtained from the different reference compounds are in excellent agreement. The presently recommended rate constant for HFC‐134a [JPL 92–20, 1992; IUPAC, 1992] is too

ISSN:0094-8276    

DOI:10.1029/93GL01336

年代:1993

数据来源: WILEY

摘要:

To monitor future global temperature trends, it would be extremely useful if parameters nonlinearly related to surface temperature could be found, thereby amplifying any warming signal that may exist. Evidence that global thunderstorm activity is nonlinearly related to diurnal, seasonal and interannual temperature variations is presented. Since global thunderstorm activity is also well correlated with the earth's ionospheric potential, it appears that variations of ionospheric potential, that can be measured at a single location, may be able to supply valuable information regarding global surface temperature fluctuations. The observations presented enable a prediction that a 1% (≈3K) increase in global surface temperatures may result in a 20% (≈50KV) increase in ionospheric potent

ISSN:0094-8276    

DOI:10.1029/93GL01774

年代:1993

数据来源: WILEY

摘要:

In the 48‐hour period of 06 UT March 12 to 06 UT March 14, 1993, the eastern United States experienced one of the most severe storms of the century, This winter storm produced over 59,000 cloud‐to‐ground flashes with a peak lightning rate exceeding 5,100 flashes per hour. Flash densities exceeded 0.16 flashes per km2in an area just south of Tampa, Florida. The overall percentage of positive flashes averaged 13.1% and positive flash percentages exceeded 60% in the northern portion of the storm as it moved over northern Florida and southern Alabama and Georgia. Median peak currents for negative flashes were 30 kA and for positive flashes 52 kA. Flash density contours followed the Gulf Stream off the coast of the Carolinas. Few lightning flashes to ground were recorded north of the Caro

ISSN:0094-8276    

DOI:10.1029/93GL01335

年代:1993

数据来源: WILEY