Dusty space plasma diagnosis using temporal behavior of polar mesospheric summer echoes during active modification

The objective of this paper is to study the effect of different plasma and dust parameters on Polar Mesospheric Summer Echoes (PMSE) temporal behavior after turn-on and turn-off of radio wave heating and to use these responses to diagnose the properties of the dust layer. The threshold radar frequency and dust parameters for the enhancement or suppression of radar echoes after radio wave heating turn-on are investigated for measured mesospheric plasma parameters. The effect of parameters such as the electron temperature enhancement during heating, dust density, dust charge polarity, ion-neutral collision frequency, electron density and dust radius on the temporal evolution of electron irregularities associated with PMSE are investigated. The possible diagnostic information for various charged dust and background plasma quantities using the temporal behavior of backscattered radar power in active experiments is discussed. The computational results are used to make predictions for PMSE active modification experiments at 7.9, 56, 139, 224 and 930MHz corresponding to existing radar facilities. Data from a 2009 VHF (224 MHz) experiment at EISCAT is compared with the computational model to obtain dust parameters in the PMSE

History of the Tromsø ionosphere heating facility

We present the historical background of the construction of a major ionospheric heating facility, “Heating”, near Tromsø, Norway, in the 1970s by the Max Planck Institute for Aeronomy; we also detail the facility’s subsequent operational history to the present. Heating was built next to the European Incoherent Scatter Scientific Association (EISCAT) incoherent scatter (IS) radar facility and in a region with a multitude of diagnostic instruments used to study the auroral region. The facility was transferred to EISCAT in January 1993 and continues to provide new discoveries in plasma physics and ionospheric and atmospheric science to this day. It is expected that Heating will continue operating along with the new generation of IS radar, called EISCAT_3D, when it is commissioned in the near future

Ionospheric electron number densities from CUTLASS dual-frequency velocity measurements using artificial backscatter over EISCAT

Using quasi-simultaneous line-of-sight velocity measurements at multiple frequencies from the Hankasalmi Cooperative UK Twin Auroral Sounding System (CUTLASS) on the Super Dual Auroral Radar Network (SuperDARN), we calculate electron number densities using a derivation outlined in Gillies et al. (2010, 2012). Backscatter targets were generated using the European Incoherent Scatter (EISCAT) ionospheric modification facility at Tromsø, Norway. We use two methods on two case studies. The first approach is to use the dual-frequency capability on CUTLASS and compare line-of-sight velocities between frequencies with a MHz or greater difference. The other method used the kHz frequency shifts automatically made by the SuperDARN radar during routine operations. Using ray tracing to obtain the approximate altitude of the backscatter, we demonstrate that for both methods, SuperDARN significantly overestimates Ne compared to those obtained from the EISCAT incoherent scatter radar over the same time period. The discrepancy between the Ne measurements of both radars may be largely due to SuperDARN sensitivity to backscatter produced by localized density irregularities which obscure the background levels

The Extending of Observing Altitudes of Plasma and Ion Lines During Ionospheric Heating

Source at https://doi.org/10.1002/2017JA024809. The ultrahigh-frequency observation during an ionospheric heating experiment on 11 March 2014 at the European Incoherent Scatter Scientific Association Tromsø site illustrated a remarkable extension of observing altitudes of the enhanced plasma line and the ion line, implying that the enhanced ion acoustic wave and Langmuir wave should satisfy the Bragg condition within the extending altitude range. An analysis shows that the dependence of the wave number of the traveling ion acoustic wave on the profiles of enhanced electron temperature and ion mass, as are expected from the dispersion relation of the ion acoustic wave, leads to the extension of observing altitudes of the enhanced ion line. In addition, the altitude extension of the enhanced plasma line is dependent mainly on the profile of the electron density, although it is not independent of the profile of the electron temperature. Considering a small gradient profile of electron density, however, the enhanced electron temperature, as well as the thermal conduction along the magnetic field, may lead to the altitude extension of the enhanced plasma line

Modulation of polar mesospheric summer echoes (PMSEs) with high-frequency heating during low solar illumination

Polar mesospheric summer echo (PMSE) formation is linked to charged dust/ice particles in the mesosphere. We investigate the modulation of PMSEs with radio waves based on measurements with EISCAT VHF radar and EISCAT heating facility during low solar illumination. The measurements were made in August 2018 and 2020 around 20:02 UT. Heating was operated in cycles with intervals of 48 s on and 168 s off. More than half of the observed heating cycles show a PMSE modulation with a decrease in PMSE when the heater is on and an increase when it is switched off again. The PMSE often increases beyond its initial strength. Less than half of the observed modulations have such an overshoot. The overshoots are small or nonexistent at strong PMSE, and they are not observed when the ionosphere is influenced by particle precipitation. We observe instances of very large overshoots at weak PMSE. PMSE modulation varies strongly from one cycle to the next, being highly variable on spatial scales smaller than a kilometer and timescales shorter than the timescales assumed for the variation in dust parameters. Average curves over several heating cycles are similar to the overshoot curves predicted by theory and observed previously. Some of the individual curves show stronger overshoots than reported in previous studies, and they exceed the values predicted by theory. A possible explanation is that the dust-charging conditions are different either because of the reduced solar illumination around midnight or because of long-term changes in ice particles in the mesosphere. We conclude that it is not possible to reliably derive the dust-charging parameters from the observed PMSE modulations

Long-term variations in electric conductivities measured by the EISCAT Tromsoe UHF radar

第6回極域科学シンポジウム[OS] 宙空圏11月16日（月）　国立極地研究所 2階 大会議

GNSS measurements of artificial ionospheric irregularities

We present observations of GNSS amplitude and TEC fluctuations to characterize artificial ionospheric irregularities generated by high-power HF experiment. The experiments were designed so that a GNSS satellite signal intersected the disturbed ionospheric volume along the local magnetic field line direction according to the experiment setup described in [1]. Compared to the previous studies [2], the presented experiments allow us to compare high-rate GNSS (20-50 Hz) parameters with the electron density and temperature deviations from the background in the F-region that are measured by an incoherent scatter radar which is co-located with a GNSS receiver. The spectrum of GNSS amplitude and TEC shows enhanced signal fluctuations when the ionosphere is heated especially in the magnetic zenith direction. We investigate GNSS signal responses to artificial ionosphere irregularities in different geophysical conditions such as peak electron density and electron temperature. It is shown that Rate of TEC (ROT) values may be used as proxy to represent the strength of ionospheric density irregularities. The experiments presented here aim to study fundamental process of GNSS signal scattering due to ionosphere irregularities by a controlled manner. References [1] H. Sato, M. T. Rietveld, and N. Jakowski, “GLONASS Observation of Artificial Field-Aligned Plasma Irregularities Near Magnetic Zenith During EISCAT HF Experiment,” Geophys. Res. Lett., vol. 48, no. 4, p. e2020GL091673, 2021, doi: https://doi.org/10.1029/2020GL091673. [2] G. Milikh, A. Gurevich, K. Zybin, and J. Secan, “Perturbations of GPS signals by the ionospheric irregularities generated due to HF-heating at triple of electron gyrofrequency,” Geophys. Res. Lett., vol. 35, no. 22, p. L22102, Nov. 2008, doi: 10.1029/2008GL035527

Dusty Space Plasma Diagnosis Using the Behavior of Polar Mesospheric Summer Echoes During Electron Precipitation Events

The behavior of polar mesospheric summer echoes (PMSEs) during an electron precipitation event is investigated by including dusty plasma effects for the first time. The observational data recorded with the very high frequency (224 MHz) and ultrahigh frequency (930 MHz) radars at the European Incoherent SCATter Scientific Association on 10 and 11 July 2012 are presented. The observed radar echoes show that the PMSEs are both correlated and anticorrelated with the increased electron density associated with electron precipitation events on the two consecutive days. The experimental observations are compared with numerical simulations of the temporal evolution of PMSE with different background dusty plasma parameters during the electron precipitation event. Specifically, the effect of dust radius, dust density, recombination/photoionization rates, photo-detachment current, and electron density enhancement ratio on the behavior of a PMSE layer and the associated dust charging process in the course of electron precipitation events is studied. It is observed that the ratio of electron density fluctuation amplitude δne to the plasma density (ne) plays a critical role in the appearance/disappearance of the layer. The simulation results revealed that the existence of PMSE is mainly determined by dust radius and dust density. The dusty plasma parameters associated with each event are estimated. The condensation nuclei of the ice particles such as proton hydrate clusters (H+(H2O)n) or meteoric smoke particles can be determined by employing the microphysical models along with the dusty plasma simulations. This can resolve any discrepancy in the description of the observed phenomena. ©2018. American Geophysical Union. All Rights Reserved

A case study of a sporadic sodium layer observed by the ALOMAR Weber Na lidar

Several possible mechanisms for the production of sporadic sodium layers have been discussed in the literature, but none of them seem to explain all the accumulated observations. The hypotheses range from direct meteoric input, to energetic electron bombardment on meteoric smoke particles, to ion neutralization, to temperature dependent chemistry. The varied instrumentation located on Andøya and near Tromsø in Norway gives us an opportunity to test the different theories applied to high latitude sporadic sodium layers. We use the ALOMARWeber sodium lidar to monitor the appearance and characteristics of a sporadic sodium layer that was observed on 5 November 2005. We also monitor the temperature to test the hypotheses regarding a temperature dependent mechanism. The EISCAT Tromsø Dynasonde, the ALOMAR/UiO All-sky camera and the SKiYMET meteor radar on Andøya are used to test the suggested relationships of sporadic sodium layers and sporadic E-layers, electron precipitation, and meteor deposition during this event. We find that more than one candidate is eligible to explain our observation of the sporadic sodium layer