Laboratory simulation of the injection of energetic electron beams into the ionosphere—Ignition of the beam plasma discharge

Experiments, which somewhat simulate the injection of monoenergetic (several keV) electron beams into the ionosphere, have been performed in the very large (17 m × 26 m) vacuum chamber at Johnson Space Center. Typical operating ranges were: Beam current, I (0–130 mA), beam energy, E (0.5–3 kV), magnetic field, (0.3–2 G), path length, L (10–20 m), and injection pitch angle, α(0–80°). Measurements were carried out in both steady state and pulsed modes. In steady state and for constant V, B, p, L, α, the beam plasma discharge (BPD) is abruptly ignited when the beam current is increased above a critical value; at currents below critical, the beam configuration appears grossly consistent with single particle behavior. If it is assumed that each of the experiment parameters can be varied independently, the critical current required for ignition obeys the empirical relationship at p < 2 × 10^?5 torr:

$\text{I}\textcolor{red}{}\text{E}{}^{\mathrm{3/2}}\text{B}{}^{\mathrm{<mtext>0.7</mtext><mtext>pL</mtext>}}$

The BPD is characterized by 1) a large increase in the plasma production rate manifested in corresponding increases in the 3914 Å light intensity and plasma density, 2) intense wave emissions in a broad band centered at the plasma frequency and a second band extending from a few kHz up to the electron cyclotron frequency, 3) scattering of the beam in velocity space and 4) radial expansion and pitch angle scattering of the primary beam leading to the disappearance of single particle trajectory features.Measurements of the BPD critical current have been carried out with an ion thruster (Kaufman engine) to provide a background plasma, and these indicate that the presence of an ambient plasma of typical ionospheric densities has little effect on the critical current relation.Measurements of wave amplitudes over a large frequency range show that the amplitude of waves near the plasma and electron cyclotron frequencies are too small to cause or sustain BPD, and that the important instabilities are at much lower frequency (～ 3 kHz in these measurements).     

Oblique sounding of the ionosphere by powerful wave beams

The article is devoted to modeling the impact on the ionosphere powerful obliquely incident wave beam. The basis of this analysis will be orbital variational principle for the intense wave beams-generalization of Fermat’s principle to the case of a nonlinear medium (, ,  and ). Under the influence of a powerful wave beam appears manageable the additional stratification of the ionospheric layer F2. Explicit expressions show how the properties of the test beam, with a shifted frequency, released in the same direction as the beam depend on the intensity of a powerful beam and the frequency shift.     

Dynamics and structure of ion clouds in the ionosphere from multifrequency doppler sounding

The evolution of a barium ion cloud formed in the MR-20 rocket experiment in the low-latitude ionosphere is considered using data of Doppler multifrequency sounding.     

The response of the ionosphere over Ilorin to some geomagnetic storms

The effects of some geomagnetic storms on the F2 layer peak parameters over Ilorin, Nigeria (Lat. 8:53°N, Long. 4.5°E, dip angle, −2.96°) have been investigated. Our results showed that the highest intensity of the noon bite-out occurred during the March equinox and lowest during the June Solstice on quiet days. Quiet day NmF2 disturbances which appeared as a pre-storm enhancement, but not related to the magnetic storm event that followed were observed at this station. These enhancements were attributed to the modification of the equatorial electric field as a result of injection of the Auroral electric field to the low and equatorial ionosphere. For disturbed conditions, the morphology of the NmF2 on quiet days is altered. Daytime and nighttime NmF2 and hmF2 enhancements were recorded at this station. Decreases in NmF2 were also observed during the recovery periods, most of which appeared during the post-noon period, except the storm event of May 28–29. On the average, enhancements in NmF2 (i.e. Positive phases) are the prominent features of this station. Observations from this study also indicate that Dst, Ap and Kp which have been the most widely used indices in academic research in describing the behavior of geomagnetic storms, are not sufficient for storm time analysis in the equatorial and low latitude ionosphere.     

The multi-wavelength study of the effect of energetic particle beams on the chromospheric emission in the 25th July 2004 solar flare

We present the multi-wavelength study of short-term variations of Hα line emission located in multiple kernels on the both sides from magnetic neutral line in the 25th July 2004 solar flare observed by VTT (Tenerife). The HXR and Hα emission in the kernels 1 and 3 is close spatially and temporally while in kernels 4 and 7 there is only delayed Hα emission observed tens seconds after HXR in the kernels 1 and 3. The locations of Hα kernels 1, 3, 4 and 7 are on the opposite sides from the magnetic neutral line. The temporal variations of Hα emission in kernels 1 and 3 coincide within 5 s with the HXR photon emission. The latter is found to have double power law photon spectra, which were corrected to a single power law with the turning point technique accounting for Ohmic losses and collisions. The Hα emission is fit by full non-LTE simulations in an atmosphere heated by an electron beam with the parameters derived from the HXR emission. The combination of radiative, thermal and non-thermal mechanisms of excitation and ionization of hydrogen atoms is considered. The temporal evolution of simulated Hα emission in the kernel 3 fits rather well the two observed intensity increases: the first at the flare onset (13:38:39–13:39:30 UT) caused by pure non-thermal excitation by beam electrons and the second one appearing after 13:40:00 UT because of a hydrodynamic heating. The observed close temporal correlation or delay of Hα emission with HXR emission points out to the precipitation either of electron (kernels 1 and 3) or protons (4 and 7).     

Self-consistent amplitude profile of ducted VLF transmitter signal due to resonant interaction with energetic electrons in the magnetosphere

Of the various sources of whistler waves in the magnetosphere, the signals from terrestrial VLF transmitters are apparently the simplest for theoretical analysis. The role of these signals in the acceleration and pitch-angle scattering of energetic electrons in the Earth’s radiation belts has not been fully studied quantitatively, despite many decades of relevant research. The main problem in studying this issue is that to calculate the acceleration and pitch-angle scattering of particles, it is necessary to know the spatial profile of the signal amplitude. This is especially critical for phase-trapped particles, for which the energy exchange with the wave is the most significant. At the same time, the wave amplitude profile itself is determined by the interaction of the wave with resonant particles. Thus, we are dealing with a self-consistent problem, which is described by a nonlinear system of equations - a kinetic equation for the distribution function of resonant particles with a self-consistent field, and an equation for the wave field, in which the nonlinear and non-local growth rate is determined by the distribution function of resonant particles. In this paper, we develop an approach to solving this system of equations and the corresponding physical problem using the method of successive approximations.     

The interaction of high-voltage spheres with the ionosphere

The interaction of a high-voltage sphere with both magnetized and unmagnetized plasmas was studied with an electrostatic fluid code. Simulations were conducted for a wide range of sphere and plasma parameters. Depending on the conditions, one can observe a propagating spherical double layer, an electron ringing, a stable rapidly-rotating electron density torus, as well as spherical and toroidal discharges.     

The global response of terrestrial ionosphere to the December 2015 space weather event

This paper investigates the ionospheric storm of December 19–21, 2015, which was initiated by two successive CME eruptions that caused a G3 space weather event. We used the in situ electron density (N_e) and electron temperature (T_e) and the Total Electron Content (TEC) measurements from SWARM-A satellite, as well as the O/N₂ observations from TIMED/GUVI to study the ionospheric impact. The observations reveal the longitudinal and hemispherical differences in the ionospheric response to the storm event. A positive ionospheric storm was observed over the American, African and Asian regions on 20 December, and the next day showed a negative storm. Both these exhibited hemispheric differences. A positive storm was observed over the East Pacific region on 21 December. It is seen that the net effect of both the disturbance dynamo electric field and composition differences become important in explaining the observed variability in topside ionospheric densities. In addition, we also discuss the T_e variations that occurred as a consequence of the space weather event.     

Electron beams and their interactions with the ionosphere — A review of the E| |B series

A review is presented of results from a series of experiments which began with an attempt to reflect electrons from the potential change which is thought to generate the aurora. In order to understand the experiment, this series then expanded to study beam-plasma interactions in the laboratory as well as in the ionosphere. Results from the electron reflection experiment, as well as in situ and ground-based observations of the waves generated by beam-plasma interactions will be reviewed. Measurements bearing on modifications of the ambient plasma by the beam-emitting rocket will be presented.     

Heat balance of the ionosphere: Implications for the international reference ionosphere

Theoretical considerations can be helpful tools in modelling ionospheric parameters in regions and for times where not enough experimental data are available. Our study asks whether results of heat balance calculations should be introduced to supplement the data base for the International Reference Ionosphere (IRI). We discuss the present status of our theoretical understanding and examine the influence of the following unresolved or neglected terms: (1) electron heating rate, (2) electron cooling by fine structure excitation of atomic oxygen, and (3) height-dependent Coulomb Logarithm. The ambiguity introduced by (1)–(3) leads up to 30% uncertainty in the electron temperature of the lower thermosphere. The electron temperature in the upper ionosphere is largely determined by heat conduction from above and depends critically on the conditions assumed at the boundary between ionosphere and plasmasphere.     

The lower ionosphere response to its disturbances by powerful radio waves

The paper presents data from some campaigns at Sura heating facility in 2011–1016. The experiments on probing of the artificial disturbed region of the lower ionosphere were carried out at two observation sites. One of them was located near Vasil’sursk 1 km from Sura facility (56.1°N; 46.1°E) and the other site was located at the Observatory (55.85°N; 48.8°E) of Kazan State University, 170 km to the East. Investigation of the features of the disturbed region of the lower ionosphere based on its diagnostics by the methods of the vertical sounding and oblique backscattering is the main goal of this paper. Ionosphere disturbance was fulfilled by the effect of the powerful radio wave of the ordinary or extraordinary polarization emitted by transmitters of the Sura facility with effective radiated power ERP = 50–120 MW at the frequency of 4.3, 4.7 and 5.6 MHz. Pumping waves were emitted with period from 30 s to 15 min. The disturbed region of the ionosphere in Vasil’sursk was probed by the vertical sounding technique using the partial reflexion radar at the frequency of 2.95 and 4.7 MHz. For the oblique sounding of the disturbed region the modified ionosonde Cyclon-M, operating at ten frequencies from 2.01 to 6.51 MHz was used at the Observatory site. On many heating sessions simultaneous variations of the probing partial reflection signals in Vasil’sursk and backscattered signals in Observatory were observed at the height at 40–100 km below the reflection height of the pumping wave. These observations were correlated with the pumping periods of the Sura facility. Possible mechanisms of the appearance of the disturbance in the lower ionosphere and its effect on the probing radio waves are discussed.     

Early and delayed reproductive death in human cells exposed to high energy iron ion beams.

The aim of this research was to determine the biological effectiveness for early and delayed effects of high energy, high linear energy transfer (LET) charged particles. Survival and delayed reproductive death were measured in AG1522 human fibroblast cells exposed to Fe-ion beams of energies between 0.2 and 1 GeV/n, 0.97 GeV/n Ti-ion and 0.49 GeV/n Si-ion beams. The cells were irradiated at the HIMAC accelerator in Chiba, Japan (0.2 and 0.5 GeV/n Fe and 0.49 GeV/n Si) and at the NASA Space Radiation Laboratory in Brookhaven, USA (1 GeV/n Fe and 0.97 GeV/n Ti ions). The dose-effect curves were measured in the dose range between 0.25 and 2 Gy. For comparison cells were exposed to 60Co gamma rays. Analysis of the dose-effect curves show that all the heavy ion beams induce inactivation and delayed reproductive death more effectively than 60Co gamma rays. The only exception is the 0.2 GeV/n Fe-ion beam at low doses. The progeny of the irradiated cells show delayed damage in the form of reproductive death with all the heavy ion beams with the 1 GeV/n Fe-ion beam being the most effective. The relative biological effectiveness at low doses of the iron beams is highest for LET values between 140 and 200 keV/micrometers with values of 1.6 and 3 for early and delayed reproductive death, respectively. Analysis of the fluence-effect curves shows that the cross-sections for early and delayed inactivation increase with increasing LET up to 442 keV/micrometers.     

Possible DC electric field in the ionosphere related to seismicity

This paper presents the method for calculation of DC electric field in the atmosphere and the ionosphere generated by model distribution of external electric current in the lower atmosphere. Appearance of such current is associated with enhancement of seismic activity that is accompanied by emanation of soil gases into the atmosphere. These gases transfer positive and negative charged aerosols. Atmospheric convection of charged aerosols forms external electric current, which works as a source of conductivity current in the atmosphere–ionosphere electric circuit. It is shown that DC electric field generated in the ionosphere by this current reaches up to 10 mV/m, while the long-term vertical electric field disturbances excited near the Earth surface do not exceed 100 V/m. Such limitation of the near-ground field is caused by the formation of potential barrier for charged particles at the Earth surface in a process of their transport from soil to atmosphere.     

Validation of the Neustrelitz Global Model according to the low latitude ionosphere

Empirical modeling including empirical model for the total electron content (TEC) is important for the study of the ionosphere and practical applications. In this paper goodness of new Neustrelitz Global Model (then NGM) at low latitudes is studied. The NGM model includes such parameters as the maximal electron density (NmF2) and altitude of the maximum (hmF2). As of today, besides NGM there are several empirical models for NmF2 and hmF2. Therefore, a comparison of these parameters of the NGM model, not only with the experimental data, but also with two versions of the International Reference Ionosphere (the IRI model): IRI2001 and IRI-Plas would be instructive. Because the NGM model incorporates special factor describing the equatorial anomaly, the comparison in lower latitude areas is particularly interesting. As one can see from the presented example of the data from low latitude stations located in the northern and southern hemispheres near the Greenwich meridian, the NGM model may have certain advantages over the IRI model versions. In particular, NGM TEC is preferable regardless of solar activity level while NGM NmF2 is only preferable under high solar activity conditions. Next, NGM equivalent slab thickness of the ionosphere: τ(NGM) = TEC(NGM)/NmF2(NGM) has been calculated and tested to answer the question whether τ(NGM) can be used as a proxy of the slab thickness of the ionosphere for an empirical modeling. The answer is positive for the near equatorial stations and periods of high solar activity, and under such conditions predicted τ(NGM) can be used for deriving NmF2 from the experimental values of TEC(CODE) in real time.     

The properties of the low altitude magnetic belt in the Venus ionosphere

When the solar wind dynamic pressure is high, the Venus ionosphere usually contains a belt of steady magnetic field at the very lowest altitudes to which Pioneer Venus probes. The current layer that flows on the high altitude side of this low altitude belt is centered at an altitude which ranges from 170 to 190 km with a most probable altitude of 182 km. This altitude is independent of solar zenith angle and hence the current system is flowing horizontally rather than vertically as proposed by Cloutier and co-workers. The lower edge of the magnetic belt was probed only on the lowest altitude passes of Pioneer Venus. This boundary is even more stable in location. The belt has decayed to 90% of its maximum strength usually by 162 km and to 50% of its maximum strength by 155 km. We interpret these data to indicate that the observed magnetic structure of the Venus ionosphere is a product of temporal evolution rather than of spacecraft motion through a spatially varying static structure.     

Operational communication systems and relationships to the ionosphere and space weather

There are a variety of operational communication systems that are dependent upon the ionosphere, and there are others that are influenced by the ionosphere. In the dependent category, we have short-wave (i.e., MF and HF systems) and long-wave systems (i.e., VLF and LF systems). In the influenced category we have some VHF systems such as meteor-burst systems, and higher frequency SATCOM systems in the UHF and SHF bands. The paper will address various resource management issues for specified operational systems, and the relationship with aspects of space-weather will be discussed. Some examples where space-weather information is used in existing systems are presented. We also identify how space-weather information could be used in those situations where it is currently unused. We conclude with challenges facing advocates of a viable space-weather program [Goodman, J.M. Space Weather and Telecommunications. Kluwer international series of Engineering and Computer Science, Springer Science + Buisness Media Inc., New York, 2005].