scholarly journals Electron heating by HF-pumping of high-latitude ionospheric F-region plasma near magnetic zenith

2019 ◽  
Author(s):  
Thomas B. Leyser ◽  
Björn Gustavsson ◽  
Theresa Rexer ◽  
Michael T. Rietveld
Keyword(s):  
Electron Temperature ◽  
Pump Beam ◽  
Electron Heating ◽  
Incoherent Scatter ◽  
F Region ◽  
Left Handed ◽  
Parameter Values ◽  
Uhf Radar ◽  
Region Plasma ◽  
Magnetic Zenith

Abstract. High frequency electromagnetic pumping of ionospheric F-region plasma at high and mid latitudes gives the strongest plasma response in magnetic zenith, antiparallel to the geomagnetic field in the northern hemisphere. This has been observed in optical emissions from the pumped plasma turbulence, electron temperature enhancements, filamentary magnetic field-aligned plasma density irregularities, and in self-focusing of the pump beam in magnetic zenith. We present results of EISCAT (European Incoherent SCATter association) Heating-induced magnetic-zenith effects observed with the EISCAT UHF incoherent scatter radar. With Heating transmitting a left-handed circularly polarised pump beam towards magnetic zenith, the UHF radar was scanned in elevation in steps of 1.0° and 1.5° around magnetic zenith. The electron energy equation was integrated to model the electron temperature and associated electron heating rate and optimized to fit the plasma parameter values measured with the radar. The experimental and modeling results are consistent with pump wave propagation in the L mode in magnetic zenith, rather than in the O mode.

scholarly journals Electron heating by HF pumping of high-latitude ionospheric F-region plasma near magnetic zenith

2020 ◽  
Vol 38 (2) ◽  
pp. 297-307 ◽  
Author(s):  
Thomas B. Leyser ◽  
Björn Gustavsson ◽  
Theresa Rexer ◽  
Michael T. Rietveld
Keyword(s):  
Electron Temperature ◽  
Pump Beam ◽  
Electron Heating ◽  
Incoherent Scatter ◽  
F Region ◽  
Left Handed ◽  
Parameter Values ◽  
Uhf Radar ◽  
Region Plasma ◽  
Magnetic Zenith

Abstract. High-frequency electromagnetic pumping of ionospheric F-region plasma at high and mid latitudes gives the strongest plasma response in magnetic zenith, antiparallel to the geomagnetic field in the Northern Hemisphere. This has been observed in optical emissions from the pumped plasma turbulence, electron temperature enhancements, filamentary magnetic field-aligned plasma density irregularities, and in self-focusing of the pump beam in magnetic zenith. We present results of EISCAT (European Incoherent SCATter association) Heating-induced magnetic-zenith effects observed with the EISCAT UHF incoherent scatter radar. With heating transmitting a left-handed circularly polarized pump beam towards magnetic zenith, the UHF radar was scanned in elevation in steps of 1.0 and 1.5∘ around magnetic zenith. The electron energy equation was integrated to model the electron temperature and associated electron heating rate and optimized to fit the plasma parameter values measured with the radar. The experimental and modelling results are consistent with pump wave propagation in the L mode in magnetic zenith, rather than in the O mode.

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 the orientation of small-scale electron density irregularities and F region plasma flow direction

2000 ◽  
Vol 18 (8) ◽  
pp. 918-926 ◽  
Author(s):  
E. D. Tereshchenko ◽  
B. Z. Khudukon ◽  
M. O. Kozlova ◽  
O. V. Evstafiev ◽  
T. Nygrén ◽  
...  
Keyword(s):  
Plasma Flow ◽  
Flow Direction ◽  
Small Scale ◽  
Incoherent Scatter ◽  
F Region ◽  
Anisotropy Parameters ◽  
Electron Density Irregularities ◽  
Region Plasma ◽  
Good Agreement ◽  
Field Aligned Irregularities

Abstract. Results are shown from an experimental campaign where satellite scintillation was observed at three sites at high latitudes and, simultaneously, the F region plasma flow was measured by the nearby EISCAT incoherent scatter radar. The anisotropy parameters of field-aligned irregularities are determined from amplitude scintillation using a method based on the variance of the relative logarithmic amplitude. The orientation of the anisotropy in a plane perpendicular to the geomagnetic field is compared with the direction of F region plasma flow. The results indicate that in most cases a good agreement between the two directions is obtained.Key words: Ionosphere (auroral ionosphere; ionospheric irregularities)

scholarly journals Evidence of <i>L</i>-mode electromagnetic wave pumping of ionospheric plasma near geomagnetic zenith

2018 ◽  
Vol 36 (1) ◽  
pp. 243-251 ◽  
Author(s):  
Thomas B. Leyser ◽  
H. Gordon James ◽  
Björn Gustavsson ◽  
Michael T. Rietveld
Keyword(s):  
Electromagnetic Waves ◽  
Ionospheric Plasma ◽  
Pump Wave ◽  
Topside Ionosphere ◽  
Mode Propagation ◽  
Pump Frequency ◽  
Density Peak ◽  
F Region ◽  
Left Handed ◽  
Magnetic Zenith

Abstract. The response of ionospheric plasma to pumping by powerful HF (high frequency) electromagnetic waves transmitted from the ground into the ionosphere is the strongest in the direction of geomagnetic zenith. We present experimental results from transmitting a left-handed circularly polarized HF beam from the EISCAT (European Incoherent SCATter association) Heating facility in magnetic zenith. The CASSIOPE (CAScade, Smallsat and IOnospheric Polar Explorer) spacecraft in the topside ionosphere above the F-region density peak detected transionospheric pump radiation, although the pump frequency was below the maximum ionospheric plasma frequency. The pump wave is deduced to arrive at CASSIOPE through L-mode propagation and associated double (O to Z, Z to O) conversion in pump-induced radio windows. L-mode propagation allows the pump wave to reach higher plasma densities and higher ionospheric altitudes than O-mode propagation so that a pump wave in the L-mode can facilitate excitation of upper hybrid phenomena localized in density depletions in a larger altitude range. L-mode propagation is therefore suggested to be important in explaining the magnetic zenith effect. Keywords. Space plasma physics (active perturbation experiments)

Analysis of incoherent scatter radar data from non-thermal F-region plasma

1989 ◽  
Vol 51 (6) ◽  
pp. 483-495 ◽  
Author(s):  
K. Suvanto ◽  
M. Lockwood ◽  
K.J. Winser ◽  
A.D. Farmer ◽  
B.J.I. Bromage
Keyword(s):  
Radar Data ◽  
Incoherent Scatter Radar ◽  
Incoherent Scatter ◽  
F Region ◽  
Scatter Radar ◽  
Region Plasma

scholarly journals Poker Flat Incoherent Scatter Radar observations of anomalous electron heating in the E region

2013 ◽  
Vol 31 (7) ◽  
pp. 1163-1176 ◽  
Author(s):  
R. A. Makarevich ◽  
A. V. Koustov ◽  
M. J. Nicolls
Keyword(s):  
Electric Field ◽  
Electron Temperature ◽  
Electric Fields ◽  
Linear Trend ◽  
Incoherent Scatter Radar ◽  
Electron Heating ◽  
Incoherent Scatter ◽  
Convection Electric Field ◽  
Scatter Radar ◽  
E Region

Abstract. A comprehensive 2-year dataset collected with the Poker Flat Incoherent Scatter Radar (PFISR) located near Fairbanks, Alaska (MLAT = 65.4° N) is employed to identify and analyse 22 events of anomalous electron heating (AEH) in the auroral E region. The overall AEH occurrence probability is conservatively estimated to be 0.3% from nearly-continuous observations of the E region by PFISR, although it increases to 0.7–0.9% in the dawn and dusk sectors where all AEH events were observed. The AEH occurrence variation with MLT is broadly consistent with those of events with high convection velocity (>1000 m s−1) or electron temperature (> 800 K), except for much smaller AEH probability and absence of AEH events near magnetic midnight. This suggests that high convection electric field by itself is necessary but not sufficient for measurable electron heating by two-stream plasma waves. The multi-point observations are utilised to investigate the fundamental dependence of the electron temperature on the convection electric field, focusing on the previously-proposed saturation effects at extreme electric fields. The AEH dataset was found to exhibit considerable scatter and, on average, similar rate of the electron temperature increase with the electric field up to 100 mV m−1 as compared with previous studies. At higher (highest) electric fields, the electron temperatures are below the linear trend on average (within uncertainty). By employing a simple fluid model of AEH, it is demonstrated that some of this deviation from the linear trend may be due to a stronger vibrational cooling at very large temperatures and electric fields.

Westward travelling surge driven by the polar cap flow channels

2021 ◽  
Author(s):  
Yuzhang Ma ◽  
Qing-He Zhang ◽  
Larry R. Lyons ◽  
Jiang Liu ◽  
Zan-Yang Xing ◽  
...  
Keyword(s):  
Electron Temperature ◽  
Flow Channel ◽  
Polar Cap ◽  
Temperature Plasma ◽  
F Region ◽  
Flow Channels ◽  
Bulge Region ◽  
Low Entropy ◽  
The Relationship ◽  
Region Plasma

&lt;p&gt;Following substorm auroral onset, the active aurora region usually expands poleward toward the poleward auroral boundary. Such poleward expansion is often associated with a bulge region that expands westward and forms the westward travelling surge (WTS). In this paper we show all-sky imager and Poker Flat Advanced Modular Incoherent Scatter Radar (PFISR) radar observations of two surge events to investigate the relationship between the surge and flow from the polar cap. For both events, we observe auroral streamers, with an adjacent flow channel consisting of decreased density and cool electron temperature plasma flowing equatorward. This flow channel appears to impinge and lead/feed surge formation, and to stay connected to the surge as it moves westward. Also, for both events, streamer observations indicate that, following initial surge development, similar flows led to explosive surge enhancements. The observation that the streamers connected to the auroral polar boundary and that the flow channels consisted of low density, low electron temperature plasma indicates that the impinging plasma came from the polar cap. For both events, the altitude variations of F region plasma within the surges are related with aurora emission and the poleward/equatorward flow, and the surges develop strong auroral streamers that initiate along the poleward auroral boundary when contacted with flow from the polar cap. These results suggest that the polar cap flow channels play a crucial role in auroral surges by feeding low entropy plasma into surge initiation and development, and also playing an important role in the dynamics within a surge.&lt;/p&gt;

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