scholarly journals The Apparent Behavior of Electron Density during an Alternating O/X-Mode Heating Experiment

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 274
Author(s):  
Zeyun Li ◽  
Qingfeng Li ◽  
Hanxian Fang ◽  
Hongwei Gong
Keyword(s):  
Electron Density ◽  
Radar Observation ◽  
Cascade Process ◽  
Mode Wave ◽  
Parametric Decay ◽  
Quantitative Calculation ◽  
Ionospheric Modification ◽  
Plasma Line ◽  
Uhf Radar ◽  
Stream Instability

We present the observations of the artificial ionospheric modification experiment of EISCAT on 18 October 2012 in Tromsø, Norway. When the pump of alternating O mode and X mode is switched on, the UHF radar observation shows some strong enhancements in electron density, ion lines and plasma lines. Based on some existing theories, we find the following: First, during the experiment, the frequency of plasma line (), ion line () and pump () matches = − 3 and = − 5 occasionally demonstrated that the cascade process occurred. Second, through quantitative calculation, we found that the O-mode component mixed in X-mode wave satisfies the thresholds of the parametric decay instability and the oscillation two-stream instability, from which we infer that the HF-induced plasma lines (HFPLs) and HF-enhanced ion lines (HFILs) observed in X-mode pulse could have been caused by the O-mode component mixed in X-mode wave. Third, the UHF radar observation shows some apparent enhancements over a wide altitude range (from approximately the reflection altitude to ~670 km) in electron density during X-mode pulse, which also does not, in fact, correspond to a true increase in electron density, but due to the enhancement in ion line or the enhancement in radar backscatter induced by some unknown mechanism.

scholarly journals Saturation and hysteresis effects in ionospheric modification experiments observed by the CUTLASS and EISCAT radars

2006 ◽  
Vol 24 (2) ◽  
pp. 543-553 ◽  
Author(s):  
D. M. Wright ◽  
J. A. Davies ◽  
T. K. Yeoman ◽  
T. R. Robinson ◽  
H. Shergill
Keyword(s):  
High Frequency ◽  
Radio Waves ◽  
Heating Facility ◽  
Ionospheric Modification ◽  
Radiated Power ◽  
Pump Waves ◽  
Hybrid Waves ◽  
Electron Density Irregularities ◽  
Uhf Radar ◽  
Field Aligned Irregularities

Abstract. The results of high latitude ionospheric modification experiments utilising the EISCAT heating facility at Tromsø are presented. As a result of the interaction between the high power pump waves and upper hybrid waves in the ionosphere, field-aligned electron density irregularities are artificially excited. Observations of these structures with the CUTLASS coherent HF radars and the EISCAT incoherent UHF radar exhibit hysteresis effects as the heater output power is varied. These are explained in terms of the two-stage mechanism which leads to the growth of the irregularities. Experiments which involve preconditioning of the ionosphere also indicate that hysteresis could be exploited to maximise the intensity of the field-aligned irregularities, especially where the available heater power is limited. In addition, the saturation of the irregularity amplitude is considered. Although, the rate of irregularity growth becomes less rapid at high heater powers it does not seem to fully saturate, indicating that the amplification would continue beyond the capabilities of the Tromsø heater - currently the most powerful of its kind. It is shown that the CUTLASS radars are sensitive to irregularities produced by very low heater powers (effective radiated powers <4 MW). This fact is discussed from the perspective of a new heating facility, SPEAR, located on Spitzbergen and capable of transmitting high frequency radio waves with an effective radiated power ~10% of that of the Tromsø heater (28MW).

scholarly journals Observations of precipitation energies during different types of pulsating aurora

2020 ◽  
Vol 38 (6) ◽  
pp. 1191-1202
Author(s):  
Fasil Tesema ◽  
Noora Partamies ◽  
Hilde Nesse Tyssøy ◽  
Derek McKay
Keyword(s):  
Electron Density ◽  
Electromagnetic Waves ◽  
Energetic Electron ◽  
Noise Absorption ◽  
Receiver Array ◽  
Maximum Electron Density ◽  
Different Types ◽  
Imaging Receiver ◽  
Cosmic Noise ◽  
Uhf Radar

Abstract. Pulsating aurora (PsA) is a diffuse type of aurora with different structures switching on and off with a period of a few seconds. It is often associated with energetic electron precipitation (>10 keV) resulting in the interaction between magnetospheric electrons and electromagnetic waves in the magnetosphere. Recent studies categorize pulsating aurora into three different types – amorphous pulsating aurora (APA), patchy pulsating aurora (PPA), and patchy aurora (PA) – based on the spatial extent of pulsations and structural stability. Differences in precipitation energies of electrons associated with these types of pulsating aurora have been suggested. In this study, we further examine these three types of pulsating aurora using electron density measurements from the European Incoherent Scatter (EISCAT) VHF/UHF radar experiments and Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) cosmic noise absorption (CNA) measurements. Based on ground-based all-sky camera images over the Fennoscandian region, we identified a total of 92 PsA events in the years between 2010 and 2020 with simultaneous EISCAT experiments. Among these events, 39, 35, and 18 were APA, PPA, and PA types with a collective duration of 58, 43, and 21 h, respectively. We found that, below 100 km, electron density enhancements during PPAs and PAs are significantly higher than during APA. However, there are no appreciable electron density differences between PPA and APA above 100 km, while PA showed weaker ionization. The altitude of the maximum electron density also showed considerable differences among the three types, centered around 110, 105, and 105 km for APA, PPA, and PA, respectively. The KAIRA CNA values also showed higher values on average during PPA (0.33 dB) compared to PA (0.23 dB) and especially APA (0.17 dB). In general, this suggests that the precipitating electrons responsible for APA have a lower energy range compared to PPA and PA types. Among the three categories, the magnitude of the maximum electron density shows higher values at lower altitudes and in the late magnetic local time (MLT) sector (after 5 MLT) during PPA than during PA or APA. We also found significant ionization down to 70 km during PPA and PA, which corresponds to ∼200 keV of precipitating electrons.

scholarly journals Simulation of Electron-Electron Two Stream Instability (ETSI)

2019 ◽  
Vol 1 ◽  
pp. 265-273
Author(s):  
F Gbaorun ◽  
E S John ◽  
T M Aper ◽  
T Daniel ◽  
F Eriba-Idoko
Keyword(s):  
Solar Wind ◽  
Electron Beam ◽  
Kinetic Energy ◽  
Electron Density ◽  
High Velocity ◽  
Electron Beams ◽  
Field Energy ◽  
Beam Velocity ◽  
Fixed Beam ◽  
Stream Instability

Stream instabilities are widely studied due to their importance in understanding astrophysical phenomena such as acceleration of high velocity of solar wind. In this work, the simulation of electron two stream instability was performed using Vorpal Simulation (VSim) code to explore the kinetic energy of plasma that arises due to the interaction between two counter-streaming electron beams at different velocities as well as different electron densities. The electron beam velocity was varied in the range of 3.58 × 106 m/s - 7.98 × 106 m/s and the resulting kinetic energy of plasma increased from 19 × 10−6J - 210 × 10−6J respectively. Also, increasing the electron density at fixed beam velocity from 1.05 × 1014m−3 - 5.84 × 1014m−3, the kinetic energy was observed to increase from 100 × 10−6J - 200 × 10−6J .However, the kinetic energy of the electron increases more with increasing beam velocity than with increasing electron density. The electric field energy which arose due to the interaction of the streaming beams did not exceed the energy of the beams.

scholarly journals Phenomena induced by powerful HF pumping towards magnetic zenith with a frequency near the F-region critical frequency and the third electron gyro harmonic frequency

2009 ◽  
Vol 27 (1) ◽  
pp. 131-145 ◽  
Author(s):  
N. F. Blagoveshchenskaya ◽  
H. C. Carlson ◽  
V. A. Kornienko ◽  
T. D. Borisova ◽  
M. T. Rietveld ◽  
...  
Keyword(s):  
Electron Density ◽  
Critical Frequency ◽  
Harmonic Frequency ◽  
Thermal Electron ◽  
Pump Frequency ◽  
Electron Heating ◽  
The Third ◽  
F Region ◽  
Uhf Radar ◽  
Magnetic Zenith

Abstract. Multi-instrument observational data from an experiment on 13 October 2006 at the EISCAT/HEATING facility at Tromsø, Norway are analysed. The experiment was carried out in the evening hours when the electron density in the F-region dropped, and the HF pump frequency fH was near and then above the critical frequency of the F2 layer. The distinctive feature of this experiment is that the pump frequency was just below the third electron gyro harmonic frequency, while both the HF pump beam and UHF radar beam were directed towards the magnetic zenith (MZ). The HF pump-induced phenomena were diagnosed with several instruments: the bi-static HF radio scatter on the London-Tromsø-St. Petersburg path, the CUTLASS radar in Hankasalmi (Finland), the European Incoherent Scatter (EISCAT) UHF radar at Tromsø and the Tromsø ionosonde (dynasonde). The results show thermal electron excitation of the HF-induced striations seen simultaneously from HF bi-static scatter and CUTLASS radar observations, accompanied by increases of electron temperature when the heater frequency was near and then above the critical frequency of the F2 layer by up to 0.4 MHz. An increase of the electron density up to 25% accompanied by strong HF-induced electron heating was observed, only when the heater frequency was near the critical frequency and just below the third electron gyro harmonic frequency. It is concluded that the combined effect of upper hybrid resonance and gyro resonance at the same altitude gives rise to strong electron heating, the excitation of striations, HF ray trapping and extension of HF waves to altitudes where they can excite Langmuir turbulence and fluxes of electrons accelerated to energies that produce ionization.

scholarly journals Comparison of F-region electron density observations by satellite radio tomography and incoherent scatter methods

1996 ◽  
Vol 14 (12) ◽  
pp. 1422-1428 ◽  
Author(s):  
T. Nygrén ◽  
M. Markkanen ◽  
M. Lehtinen ◽  
E. D. Tereshchenko ◽  
B. Z. Khudukon ◽  
...  
Keyword(s):  
Electron Density ◽  
Meridional Plane ◽  
Incoherent Scatter ◽  
The North ◽  
F Region ◽  
First Results ◽  
The Difference ◽  
A Chain ◽  
Set Up ◽  
Uhf Radar

Abstract. In November 1995 a campaign of satellite radiotomography supported by the EISCAT incoherent scatter radar and several other instruments was arranged in Scandinavia. A chain of four satellite receivers extending from the north of Norway to the south of Finland was installed approximately along a geomagnetic meridian. The receivers carried out difference Doppler measurements using signals from satellites flying along the chain. The EISCAT UHF radar was simultaneously operational with its beam swinging either in geomagnetic or in geographic meridional plane. With this experimental set-up latitudinal scans of F-region electron density are obtained both from the radar observations and by tomographic inversion of the phase observations given by the difference Doppler experiment. This paper shows the first results of the campaign and compares the electron densities given by the two methods.

scholarly journals Observations of precipitation energies during different types of pulsating aurora

2020 ◽  
Author(s):  
Fasil Tesema ◽  
Noora Partamies ◽  
Hilde Nesse Tyssøy ◽  
Derek McKay
Keyword(s):  
Electron Density ◽  
Electromagnetic Waves ◽  
Energetic Electron ◽  
Noise Absorption ◽  
Receiver Array ◽  
Maximum Electron Density ◽  
Different Types ◽  
Imaging Receiver ◽  
Cosmic Noise ◽  
Uhf Radar

Abstract. Pulsating aurora (PsA) is a diffuse type of aurora with different structures switching on and off with a period of few seconds. It is often associated with energetic electron precipitation (10 keV) resulted in the interaction between magnetospheric electrons and electromagnetic waves in the magnetosphere. Recent studies categorize pulsating aurora into three different types: amorphous pulsating aurora (APA), patchy pulsating aurora (PPA), and patchy aurora (PA) based on the spatial extent of pulsations and structural stability. Differences in precipitation energies of electrons associated with these types of pulsating aurora have been suggested. In this study, we further examine these three types of pulsating aurora using electron density measurements from the European Incoherent Scatter (EISCAT) VHF/UHF radar experiments and Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) cosmic noise absorption (CNA) measurements. Based on ground-based all-sky camera images over the Fennoscandian region, we identified a total of 92 PsA events in the years between 2010 and 2020 with simultaneous EISCAT experiments. Among these events, 39, 35, and 18 were APA, PPA, and PA types with a collective duration of 58 hrs, 43 hrs, and 21 hrs, respectively. We found that below 100 km, electron density enhancements during PPAs and PAs are significantly higher than during APA. However, there are no appreciable electron density differences between PPA and APA above 100 km, while PA showed weaker ionization. The altitude of the maximum electron density also showed considerable differences among the three types, centered around 110 km, 105 km, and 105 km for APA, PPA, and PA, respectively. The KAIRA CNA values also showed higher values on average during PPA (0.33 dB) compared to PA (0.23 dB) and especially APA (0.17 dB). In general, this suggests that the precipitating electrons responsible for APA have a lower energy range compared to PPA and PA types. Among the three categories, the magnitude of the maximum electron density shows higher values during PPA at lower altitudes and in the late MLT sector (after 5 MLT). We also found significant ionization down to 70 km during PPA and PA, which corresponds to ~ 200 keV energies of precipitating pulsating aurora electrons.

scholarly journals Climatological features of electron density in the polar ionosphere from long-term observations of EISCAT/ESR radar

2007 ◽  
Vol 25 (12) ◽  
pp. 2561-2569 ◽  
Author(s):  
H. T. Cai ◽  
S. Y. Ma ◽  
Y. Fan ◽  
Y. C. Liu ◽  
K. Schlegel
Keyword(s):  
Solar Cycle ◽  
Electron Density ◽  
Solar Maximum ◽  
Cycle Phase ◽  
Soft Particle ◽  
Winter Anomaly ◽  
Uhf Radar ◽  
Time Sector ◽  
Maximum Minimum

Abstract. In this paper, climatological features of the polar F2-region electron density (Ne) are investigated by means of statistical analysis using long-term observations from the European Incoherent Scatter UHF radar (called EISCAT in the following) and the EISCAT Svalbard radar (ESR) during periods of quiet to moderate geomagnetic activity. Field-aligned measurements by the EISCAT and ESR radars operating in CP-1 and CP-2 modes are used in this study, covering the years 1988–1999 for EISCAT and 1999–2003 for ESR. The data are sorted by season (equinox, summer and winter) and solar cycle phase (maximum, minimum, rising and falling). Some novel and interesting results are presented as follows: (1) The well-known winter anomaly is evident during the solar maximum at EISCAT, but it dies out at the latitude of the ESR; (2) The daytime peaks of Ne at EISCAT for all seasons during solar maximum lag about 1–2 h behind those at ESR, with altitudes about 10–30 km lower. (3) In addition to the daytime peak, it is revealed that there is another peak just before magnetic midnight at ESR around solar maximum, especially in winter and at equinox. The day-time ionization peak around magnetic noon observed by ESR can be attributed to soft particle precipitation in the cusp region, whereas the pre-midnight Ne maximum seems likely to be closely related to substorm events which frequently break out during that time sector, in particular for the winter case. (4) Semiannual variations are found at EISCAT during solar minimum and the falling phase of the solar cycle; at the rising phase, however, the EISCAT observations show no obvious seasonal variations.

Sign in / Sign up

Export Citation Format

Share Document