The neutral-pion decay and the gamma radiation from our Galaxy
Neutral pion decay and galactic gamma radiation from demodulated cosmic ray spectrum, discussing neutral pion meson production
Cavallo, G.↗
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The stable auroral red arc of October 31 - November 1, 1968 and its interaction with the neutral atmosphere
Satellite observations of electron temperature and the topside electron density structure are used to calculate the red arc according to the thermal conduction model. In this model, energy from the magnetosphere flows in the electron gas along geomagnetic field lines into the ionosphere. This energy heats the ambient F-region electrons sufficiently to excite the oxygen atoms to the O I(1D) level by collisional impact giving rise to the 6300 A emission characteristic of the arc. For the 31 October/1 November 1968 red arc, the calculated emission rate, geographical position, and horizontal extent of the red arc are in agreement with the photometric data obtained by airglow observatories. Almost all of the energy conducted into the red arc is ultimately transferred to the neutral gas through elastic and inelastic collisions. This energy drives a large thermal cell and the circulation extends the influence of the arc thousands of kilometers beyond the region of direct heat input. The calculated neutral gas temperature response to electron heating within the arc is small.
Roble, R. G.↗
Ionosphere heating by neutral gas winds
Investigation of the ion and electron temperature rises caused by friction between the neutral gas winds and the plasma of the ionosphere. The results obtained indicate that within an altitude range of 150-200 km, ion temperatures can exceed electron temperatures by as much as 130 K. Ion temperature increases range from 50 to 200 K, depending upon the atmosphere model used. It is pointed out that failure to make allowance for heating by friction in determinations of neutral gas temperature may lead to considerable errors.
Stubbe, P.↗
Neutral composition variation above 400 kilometers during a magnetic storm.
Examination of data from the neutral atmospheric composition experiment launched aboard Ogo 6, June 5, 1969, for the period from Sept. 27 through Oct. 3, 1969. Several magnetic storms occurred during this time, and the response of the neutral atmosphere to the energy deposition causing these storms was studied. The data indicate that the major portion of the energy is deposited at high latitudes, causing enhancements in N2 densities corresponding to Jacchia (1970) temperature increases on the order of 400 to 500 K. The time difference between atmospheric response and magnetic activity appears to be very short at high latitudes. The O/N2 ratio variations suggest dynamic processes that cause a circulation in the atmosphere that is upward at the pole with subsidence at the equator.
Taeusch, D. R.↗
The chemistry of neutral species in the D and E regions.
The photodissociation of molecular species such as oxygen, nitrogen, and water vapor in the upper atmosphere leads to the formation of a reservoir of chemical energy consisting of highly reactive atomic gases. The reactions of these with each other, and with the rest of the atmosphere, give a complex neutral chemistry involving many species and reactions. Local equilibrium can rarely be assumed for these reactions; transport by the horizontal and vertical mean flow, by eddy diffusion, and by molecular diffusion has quite different effects on the various constituents, depending on the time constants. The entire subject of the neutral chemistry in the D and E regions (between 50 and 160 km altitude) is reviewed, and related to existing experimental results. Needs for further research on the subject are indicated.
Bowhill, S. A.↗
Structure of coronal neutral sheets
A qualitative model for the structure of the neutral sheet lying along the axis of coronal streamers is developed. The internal topology of the sheet is that of extremely thin magnetic tongues greatly distended outward by the solar wind expansion inside the sheet. Due to finite conductivity effects, expansion is taking place across the field lines but is retarded relative to the external flow by the reverse jxB force. The sheet thickness is determined by three considerations: the electrical conductivity that specifies the magnitude of the gradients in field strength, the expansion velocity that stretches the field lines outward decreasing the sheet thickness, and finally, the lateral pressure balance that limits the approach of the oppositely directed external field toward the neutral plane. If sigma is the electrical conductivity, the sheet thickness is shown to be proportional to sigma-1/3. For an electron conductivity evaluated perpendicular to the internal field in the sheet, the thickness is of the order of 100 km in the inner corona and 10,000 km at 1 AU. Microturbulence and instabilities are expected to yield dimensions greater than these theoretical values since these effects tend to reduce the effective conductivity.
Pneuman, G. W.↗
Neutral winds above 200Km at high latitudes
Motion from multiple chemical releases between 200 and 300 km from 15 rockets launched from 4 high latitude locations are analyzed. The observations in the evening and midnight hours at magnetic altitudes or = 65 deg suggest that in these regions ion drag is the dominant force in driving neutral winds between 200 and 300 km. This conclusion is based on both the agreement between ion and neutral drift directions, and the fact that there are distinct changes in the wind associated with (a) the reversal in east-west ion drift at the Harang discontinuity, and (b) the transition from auroral belt, sunward ion drift and polar cap, anti-solar ion drift.
Meriwether, J. W.↗
A class of neutral functional differential equations.
Formulation and study of the initial value problem for neutral functional differential equations. The existence, uniqueness, and continuation of solutions to this problem are investigated, and an analysis is made of the dependence of the solutions on the initial conditions and parameters, resulting in the derivation of a continuous dependence theorem in which the fundamental mathematical principles underlying the continuous dependence problem for a very general system of nonlinear neutral functional differential equations are separated out.
Melvin, W. R.↗
Topologies for neutral functional differential equations.
Bounded topologies are considered for functional differential equations of the neutral type in which present dynamics of the system are influenced by its past behavior. A special bounded topology is generated on a collection of absolutely continuous functions with essentially bounded derivatives, and an application to a class of nonlinear neutral functional differential equations due to Driver (1965) is presented.
Melvin, W. R.↗
Magnetic control of the near equatorial neutral thermosphere.
Neutral density data between 400 and 500 km obtained with the Ogo 6 neutral mass spectrometer indicate that at all longitudes the daytime N2 and O densities have latitudinal minimums at the magnetic equator that are about 20 and 10%, respectively, below maximums observed between plus and minus 20 deg magnetic latitude. Our calculations suggest that this anomaly could result from latitudinal variations in ion drag associated with the 'equatorial anomaly' in F region ionization. At latitudes of enhanced electron density the energy flow from the dayside to the nightside of the earth is damped, and thus the amplitude of the temperature and density variations is enhanced, and the time of maximum is shifted to later local times.
Hedin, A. E.↗
A neutral-atmosphere composition experiment for the Atmosphere Explorer-C, -D, and -E.
The neutral-atmosphere composition experiment instrumentation is designed to obtain in-situ measurements of neutral thermosphere composition from Atmosphere Explorer-C, -D, and -E. The system is based on previously flown OGO-6 and San Marco-3 composition instruments. The mass-spectrometer sensor includes a gold-plated thermalizing chamber and ion source, a hyperbolic rod quadrupole analyzer, and an off-axis electron multiplier. Automatic ion-source sensitivity control and pulse-counting techniques provide density measurement capability from approximately 125 to 1000 km altitude. The normal operating mode includes measurement at all masses in the range of 1 to 44 amu, with emphasis on hydrogen, helium, oxygen, nitrogen, and argon.
Pelz, D. T.↗
Guiding center model to interpret neutral particle analyzer results
The theoretical model is discussed, which accounts for drift and cyclotron components of ion motion in a partially ionized plasma. Density and velocity distributions are systematically precribed. The flux into the neutral particle analyzer (NPA) from this plasma is determined by summing over all charge exchange neutrals in phase space which are directed into apertures. Especially detailed data, obtained by sweeping the line of sight of the apertures across the plasma of the NASA Lewis HIP-1 burnout device, are presented. Selection of randomized cyclotron velocity distributions about mean azimuthal drift yield energy distributions which compared well with experiment. Use of data obtained with a bending magnet on the NPA showed that separation between energy distribution curves of various mass species correlate well with a drift divided by mean cyclotron energy parameter of the theory. Use of the guiding center model in conjunction with NPA scans across the plasma aid in estimates of ion density and E field variation with plasma radius.
Englert, G. W.↗
Neutral-pion-decay gamma rays from the Galaxy and the interstellar gas content
Knowledge of the total gamma-ray production rate per H atom from the decay of neutral pions produced in interstellar cosmic-ray interactions is essential for determining the possible amount of interstellar H2. This production rate is recalculated here using the latest accelerator data on neutral pion production in p-p interactions up to about 1500 GeV. A simple but accurate approximation used here resolves the past disagreement over the magnitude of this rate. An upper limit is obtained of (1.51 plus or minus 0.23) times 10 to the -25th power/sec, consistent with the observed upper limit of 1.6 times 10 to the -25th power/sec.
Stecker, F. W.↗
Neutral-pion decay gamma rays from the galaxy and the interstellar gas content
The total gamma-ray production rate per H atom from the decay of neutral pions produced in interstellar cosmic-ray interactions is recalculated here using the latest accelerator data on the production of neutral pions in pp interactions up to 300 GeV. A simple but accurate approximation used here resolves the past disagreement over the magnitude of this rate. An upper limit is obtained for this rate by considering a maximum galactic cosmic-ray spectrum taking modulation into account.
Stecker, F. W.↗
A field-ionization neutral-particle mass spectrometer
Description of laboratory model of a neutral-particle mass spectrometer that could make localized direct measurements of the neutral densities at 1 AU. Using a magnet that has a circular pole face 2.54 cm in diameter and a gap flux density of 8.0 kG, the following sensitivities were obtained for the various species: 10 to the 10th power counts per second per Torr for H2, 3 times 10 to the eighth power counts per second per Torr for He, and 2 times 10 to the 9th power counts per second per Torr for N2. Overall sensitivity may be increased through the use of electrostatic focusing elements between the ion source and the magnetic analyzer.
Curtis, C. C.↗
The interaction between an impact-produced neutral gas cloud and the solar wind at the lunar surface
On Apr. 15, 1970, the Apollo 13 S-IVB stage impacted the nighttime lunar surface. Beginning 20 sec after impact, the Suprathermal Ion Detector Experiment and the Solar Wind Spectrometer observed a large flux of positive ions (maximum flux of about 3 x 10 to the 8th ions/sq cm/sec/ster) and electrons. Two separate streams of ions were observed: a horizontal flux that appeared to be deflected solar wind ions and a smaller vertical flux of predominantly heavy ions (greater than 10 amu), which probably were material vaporized from the S-IVB stage. An examination of the data shows that collisions between neutral molecules and hot electrons (50 eV) were probably an important ionization mechanism in the impact-produced neutral gas cloud. These electrons, which were detected by the Solar Wind Spectrometer, are thought to have been energized in a shock front or some form of intense interaction region between the cloud and the solar wind. Thus strong ionization and acceleration are seen under conditions approaching a collisionless state.
Lindeman, R. A.↗
Observations of neutral winds in the auroral E region during the magnetospheric storm of August 3-9, 1972
Auroral zone E-region neutral winds have been derived from simultaneous measurements of ion drift velocities in different altitudes by the incoherent radar facility at Chatanika, Alaska, on a quiet day before and during the great magnetospheric storm of Aug. 3-9, 1972. The neutral wind expected for a day-night pressure asymmetry appears to be strongly opposed by ion drag and local pressure gradients in the auroral oval.
Brekke, A.↗
Plasma wave turbulence at distant crossings of the plasma sheet boundaries and the neutral sheet
The orbit of IMP 7 frequently takes the spacecraft across the neutral sheet in the geomagnetic tail at a downstream distance of about 35 earth radii. This preliminary report discusses the detection of strong low-frequency electromagnetic signals and moderate electrostatic noise enhancements near local midnight. Data used were obtained during a substorm period on Oct. 28, 1972, when there were multiple crossings of the neutral sheet and the boundary of the plasma sheet.
Scarf, F. L.↗