High frequency electromagnetic radiation in CRRES geostationary injections

It is shown that experiments with geostationary injections of dense barium plasma clouds after CRRES program presented a unique opportunity for investigation of Earth's space environment radiation generation mechanism at frequencies 100 to1000 times higher than the usual plasma frequency signal. We present electromagnetic noise or radiostorm data obtained in Havana in broad frequency bands 45–90 MHz, 235MHz and 280 MHz after Ba injection. It is proposed that signals appearing with 7 to 10 min delay after injection possibly caused a substorm initiated by the injection, during which the radiation is generated by local energetic particles flowing through the irregular barium cloud. Another possibility is connected with irradiation of the barium cloud by the Jicamarca radar. Modulation of radioburst at barium gyrofrequency is typical for both cases.     

On the planetary ionospheric vortex electric fields

The paper presents a physical mechanism of large-scale vortex electric field generation in the ionospheric E- and F-layers. It shows that the planetary-scale, synoptic short-period (from several second to several hours) and fast processes (with propagation velocity higher than 1 km/s) produce a planetary-scale internal vortex electric field. Its value may far exceed that of the dynamo-field generated in the same ionospheric layer by local wind motion. We found, that an ionospheric source of the vortex electric field is spatial inhomogeneity of the geomagnetic field.     

The collective gyration of a heavy ion cloud in a magnetized plasma

In both the ionospheric barium injection experiments CRIT I and CRIT II, a long-duration oscillation was seen with a frequency close to the gyro frequency of barium and a time duration of about one second. A model for the phenomenon which was proposed for the CRIT 1 experiment is here compared to the results from CRIT II which made a much more complete set of measurements. The model follows the motion of a low-β ion cloud through a larger ambient plasma. The internal field of the model is close to antiparallel to the injection direction v_i but slightly tilted towards the self-polarization direction E_P = −v_ixB. As the ions move across the magnetic field, the space charge is continuously neutralized by magnetic-field aligned electron currents from the ambient ionosphere, drawn by the divergence in the perpendicular electric field. These currents give a perturbation of the magnetic field related to the electric field perturbation by ΔE/ΔB ≈ V_a. The model predictions agree quite well with the observed vector directions, field strengths, and decay times of the electric and magnetic fields in CRIT II. The possibility to extend the model to the active region, where the ions are produced in this type of self-ionizing injection experiments, is discussed.     

Impact of heliogeophysical disturbances on ionospheric HF channels

The article presents the results of the observation of a strong magnetic storm and two X-ray flares during the summer solstice in 2015, and their impact on the HF signals characteristics in ionospheric oblique sounding. It was found that the negative phase of the magnetic storm led to a strong degradation of the ionospheric channel, ultimately causing a long blackout on paths adjacent to subauroral latitudes. On mid-latitude paths, the decrease in 1FMOF reached ～50% relative to the average values for the quiet ionosphere. It is shown that the propagation conditions via the sporadic Es layer during the magnetic storm on a subauroral path are substantially better than those for F-mode propagation via the upper ionosphere. The delay of the sharp decrease in 1FMOF during the main phase of the magnetic storm allowed us to determine the propagation velocity of the negative phase disturbances (～100 m/s) from subauroral to mid-latitude ionosphere along two paths: Lovozero – Yoshkar-Ola and Cyprus – Nizhny Novgorod. It is shown that both the LOF and the signal/noise ratio averaged over the frequency band corresponding to the propagation mode via the sporadic Es layer correlate well with the auroral AE index. Using an over-the-horizon chirp radar with a bistatic configuration on the Cyprus – Rostov-on-Don path, we located small-scale scattering irregularities responsible for abnormal signals in the region of the equatorial boundary of the auroral oval.     

CRIT II electric, magnetic, and density observations in an ionizing neutral jet

Measurements inside a high velocity neutral barium beam show a factor of six increase in plasma density in a moving ionizing front. This region was co-located with intense electric fields (δE ≈ 300 mV/m²) perpendicular to the local geomagnetic field and field aligned currents all fluctuating at frequencies well under the lower hybrid frequency for barium but above the oxygen cycloton frequency. It was determined that these structures were moving with the barium stream near the neutral barium velocity. Large quasi-dc electric and magnetic field fluctuations were also detected. The heart of the ionizing front, a cross beam current of nearly 10 mA/m², was estimated from the magnetic field variation. This is three orders of magnitude higher than typical auroral zone currents associated with auroral arcs. This current sheet was co-located with fluxes of soft electrons which saturated the particle detector. An Alfvén wave with a finite electric field component parallel to the geomagnetic field was observed to propagate along B_o where it was detected by an instrumented sub-payload.     

Supertyphoon Hagibis action in the ionosphere on 6–13 October 2019: Results from multi-frequency multiple path sounding at oblique incidence

The purpose of the present paper is to describe the observations of the variations in the parameters of HF radio waves propagating through the ionosphere when the action of the super typhoon Hagibis on 6–13 October 2019 occurred. The observations have been made with the Harbin Engineering University (the People's Republic of China) multi-frequency multiple path radio system involving the software-defined technology. The action of the super typhoon has been shown to be accompanied by enhanced atmospheric wave activity acting to generate wave processes with periods of 10 to 120 min. Coupling in the atmosphere–upper-atmosphere–ionosphere system has been confirmed to be carried out with atmospheric gravity waves. The ionosphere underwent the greatest impact on those days when the supertyphoon had maximum energy, on 8, 10, and especially 9 October 2019, and when it was found to be in an ～2,500–3,000-km distance range from the propagation path midpoints. Under the action of wave processes, the height of the reflection region was observed to oscillate within the ±(30–90 km) limits. The amplitude of the quasi-periodic variations in the ionospheric F-region electron density was estimated to be 10–12% for periods of ～20 min, and 30–60% for periods of ～60–120 min. The joint action of the dusk terminator and the supertyphoon has been confirmed to enhance wave activity in the ionosphere. Similar effects for the dawn terminator have not been detected.     

Auroral signatures of transient processes in the outer magnetosphere

We present an analysis of sporadic and recurrent injections of magnetospheric ions in the midnight auroral oval during substorms and of the associated ionospheric ion outflows. The source of plasma sheet precipitating ions is determined using a simple method, based on the measured relation between the ion inverse velocity and time (l = v × t). This method is applied here to two typical passes of the Interball-Auroral (IA) satellite at distances of 3 R_E above the auroral regions. Substorm related ion injections are shown to be mainly due to time of flight effects. In contrast with particle trajectory computations (Sauvaud et al., 1999), the inverse velocity method does not require magnetic and electric field models and can thus be used systematically for the detection of time of flight dispersed ion structures (TDIS). This allowed us to build a large database of TDIS events and to perform a statistical analysis of their spatial distribution. For the cases presented here the source region of the injected ions is found at radial distances from 18 to 30 R_E near the equatorial magnetosphere. At Interball altitudes ( 3 R_E), ion injections detected at the poleward boundary of the nighside auroral oval are associated with shear Alfvén waves superimposed over large-scale quasi-static current structures. We show that the most poleward TDIS are collocated with a large outflow of ionospheric H⁺ and O⁺ displaying pitch-angle distributions peaked in the pitch-angle range 90°–120°. These ions are thus accelerated perpendicularly to the magnetic field not only in the main auroral acceleration region but also up to at least 3 R_E. The expanding auroral bulge thus constitutes a significant source of H⁺ and O⁺ ions for the mid-tail magnetosphere.     

Alfven echo of giant ground loop current

Here are presented experimental results concerning the registration by ground magnetometers of artificial MHD echo generated by powerful pulse current in ground loop contour. Data analysis was made of several magnetic stations for 16 experiments with giant loop-current contour giving magnetic flux 10⁶nT/km² (the current attained 20 kA). Only several rather weak bursts were registered which appeared 78±2s after main switch impulse. Echo signal was a few nanotesla. Taking into account real magnetosphere tube configuration for L ≈ 5,5 and Kp≤2 it was shown that the signal with such a delay corresponds to propagation of artificial excited Alfven echo, returning back from a magnetoconjugate ionospheric region. Meanwhile, the amplitude exceed by one order the theoretically calculated one.     

Ionospheric wave processes during HF heating experiments

Effects of ionospheric modification produced by powerful high frequency radio waves are studied using the method of field-aligned scattering of diagnostic HF radio signals. Observations of scattered HF signals have been made by the Doppler spectrum method. Analysis of the experimental data shows the appearance of quasiperiodic variations in Doppler frequency shift f_d, with periods 30–60 s during the heating cycles. Powerful HF waves are assumed to excite the Alfvén resonator generating oscillations of the magnetic field lines in the heated region and giving rise to f_d artificial variations and magnetic pulsations. In the case of continuous action of the powerful HF transmitter ionospheric waves are sometimes observed with periods 12–25 min, typical of medium-scale travelling ionospheric disturbances.     

Appearance of VLF and ELF-noises in topside ionosphere under the action of high power radio wave from data of satellite intercosmos-24

Results of a satellite experiment are presented on detection of VLF and ELF-waves excited by irradiation of the night ionosphere F-region by the field of a nonmodulated high-power radio wave. The excited VLF and ELF-waves have been detected at the topside ionosphere heights h=500–1000 km in the frequency bands 8 kHz相似文献   

Rare observation of daytime whistlers at very low latitude (L = 1.08)

The source region and propagation mechanism of low latitude whistlers (Geomag. lat. <30°) have puzzled scientific community for last many decades. In view of recent reports, there is consensus on the source region of low latitude whistlers in the vicinity of the conjugate point. But the plausible conditions of ionospheric medium through which they travel are still uncertain. In addition to that, the whistlers in daytime are never observed at geomagnetic latitudes less than 20°. Here, for the first time, we present a rare observations of whistlers during sunlit hours from a very low-latitude station Allahabad (Geomag. Lat: 16.79°N, L = 1.08) in India on 04 February 2011. More than 90 whistlers are recorded during 1200–1300 UT during which the whole propagation path from lightning source region to whistler observation site is under sunlit. The favorable factors that facilitated the whistlers prior to the sunset are investigated in terms of source lightning characteristics, geomagnetic and background ionospheric medium conditions. The whistler activity period was found to be geomagnetically quiet. However, a significant suppression in ionospheric total electron content (TEC) compared to its quiet day average is found. This shows that background ionospheric conditions may play a key role in low latitude whistler propagation. This study reveals that whistlers can occur under sunlit hours at latitudes as low as L = 1.08 when the source lightning and ionospheric medium characteristics are optimally favorable.     

基于GPS的广州地区电离层不规则体纬向漂移速度计算分析

利用广州站组建的两台短间距GPS电离层闪烁监测仪的观测数据, 分别对GPS卫星信号强度用功率谱和短间距台链互相关性两种方法计算了3次闪烁事件电离层不规则体的漂移速度. 分析结果表明, 同一不规则体会引起两台站闪烁事件的同时发生, 两种方法测量不规则体漂移速度通常在50～160m/s之间, 平均大小均在120m/s左右, 且纬向漂移速度在闪烁初期起伏较明显, 速度随闪烁时间有下降的趋势, 夜间纬向漂移方向由西向东, 广州地区漂移速度特性符合低纬其他地区不规则体漂移速度特征, 两种计算方法合理有效.      

Modeling of artificial plasma “bubble” in ionosphere

Results of a combination of radio-crossing and in situ measurements of plasma density in an artificial plasma “bubble” in the ionosphere are presented. Shaped — charge barium injection was made at short distance (≤50 m) to plasma diagnostics on the rocket. After injection the rocket passed through expanding plasma shell. Plasma density depletion inside was more than one order and plasma enhancements on the boundary about 3–5 times that of background. When the rocket passed the shell and went away by 2.1 km an abrupt drop of telemetry signal level (≤ 65 dB) was registered though plasma density was not more than 3×10³sm⁻³. An estimation of high frequency signal refraction on the plasma shell is in good accordance with refraction data of geostationary satellite signals on equatorial bubbles.     

Studying characteristics of traveling ionospheric disturbances using U-shaped traces on vertical incidence ionograms

This paper presents a case study when due to the descending additional U-shaped trace on vertical incidence ionograms, increased critical frequency stabilizes. This corresponds to an ionospheric disturbance that moves toward the ionosonde and then stays overhead.Within a 2D model, traveling ionospheric disturbances (TIDs) are superimposed on the inverted background ionosphere. So ray tracing is used to obtain propagation paths through non-stratified ionosphere thus synthesizing the disturbed ionogram traces. Investigated are changes in the cusp shape caused by varying TID parameters. A cusp-fitting method to determine the TID amplitude, spatial scale, and horizontal drift velocity are shown.     

磁尾静电离子束流-密度漂移不稳定性的数值研究

本文研究了磁尾等离子体片边界层宽频带静电噪声的产生机制.模型等离子体由暖的背景电子、暖的向地球方向的离子束流和较冷的向尾方向的离子束流组成.结果表明,静电离子束流-密度漂移不稳定性可以在比较宽的频率范围内激发,在低频区大传播角方向上增长率最大,在高频区小传播角方向上增长率也比较大。最大增长率的方向取决于离子束流和密度漂移的速度比值.这些结果与磁尾观测到的宽频带静电噪声特征符合一致.      

Registration of ELF waves in rocket-satellite experiment with plasma injection

Two rocket experiments KOMBI-SAMA with plasma injection at height 100–240 km were performed in August 1987 in the region of Brazilian magnetic anomaly (L = 1.25). The launching time of the rocket was determined so that plasma injection was at the time when satellite COSMOS 1809 passed as close as possible to magnetic tube of injection. Caesium plasma jet was produced during ≥ 300 s by electric plasma generator separated from the payload. By diagnostic instruments on board of the rocket and the satellite were registered energetic particle fluxes and plasma wave activities stimulated by plasma injection. When the satellite passed the geomagnetic tube intersecting the injection region an enhancement of ELF emission at 140 Hz, 450 Hz by 2 times was registered on board the satellite. An enhancement of energetic particles (E > 40 keV) flux by 4–5 times was registered on board the rocket. Observed ELV emission below 100 Hz is interpreted as generation of oblique electromagnetic ion-cyclotron waves due to drift plasma instability at the front of the plasma jet.     

1958年7月8日磁暴的电离层响应

本文用遍布全球的52个电离层垂测台站资料,研究1958年7月8日磁暴期间全球电离层扰动的发展变化;各扇区的响应特性;扰动的传播轨迹及速度等。获得以下结果:1.几大扇区的电离层扰动始于南北两极,美洲扇区除具这一特征外,其赤道地区在磁暴急始后不久,出现一个扰动中心,邻近区域的扰动受其控制。2.扰动由高纬向低纬发展,由扰动中心向外传播。3.扰动峰面几乎与地磁力线垂直,即扰动沿磁力线方向发展,其传播速度大约在150—600m/s范围。     

Prompt effects of solar wind variations on the inner magnetosphere and midlatitude ionosphere

It is well known that the solar wind can significantly affect high-latitude ionospheric dynamics. However, the effects of the solar wind on the middle- and low-latitude ionosphere are much less studied. In this paper, we report observations that large perturbations in the middle- and low-latitude ionosphere are well correlated with solar wind variations. In one event, a significant (20–30%) decrease of the midlatitude ionospheric electron density over a large latitudinal range was related to a sudden drop in the solar wind pressure and a northward turning of the interplanetary magnetic field, and the density decrease became larger at lower latitudes. In another event, periodic perturbations in the dayside equatorial ionospheric E × B drift and electrojet were closely associated with variations in the interplanetary electric field. Since the solar wind is always changing with time, it can be a very important and common source of ionospheric perturbations at middle- and low-latitudes. The relationship between solar wind variations and significant ionospheric perturbations has important applications in space weather.     

Dynamics of the convection in the inner magnetosphere by observations of the diffuse aurora,SAR arc and ionospheric drift

The first results of the comparison of subauroral luminosity dynamics in 557,7 and 630,0 nm emission with simultaneous measurements of the ionospheric drift in the F2 region with a digisonde DPS-4 at the Yakutsk meridian (CGMC: 55–60N, 200°E) at Kp = 2–6 are presented. It is shown from the analysis of individual events that during the magnetospheric convection intensification after the turn of the IMF B_z – component to the south the equatorward extension of diffuse aurora takes place. At the same time the westward ionospheric drift velocity increases both in the diffuse aurora region and much equatorward of it due to the occurrence of the northward polarization electric field. We suppose that the generation of polarization field can be associated with the development of the region 2 FAC during the intensification of magnetospheric convection. The comparison of ground-based observations with measurements of the plasma drift aboard the DMSP-F15 satellite has been carried out.     

Sources and losses of ring current ions: An update

The cleft ion fountain has been identified as a prodigious source of upflowing suprathermal ionospheric plasma. Modeling efforts have traced the path of these ions from the polar ionosphere along trajectories where the ions are energized to keV energies and deposited in the near earth plasma sheet. Mass and energy dispersion of these ions accounts in a natural way for the observed variation in heavy ion content of the plasma sheet. Observations of ion composition in the plasma sheet by the AMPTE and ISEE spacecraft establish that ionospheric ions dominate in the near earth plasma sheet but solar wind ions become significant tailward. The heavy ion content of the plasma sheet increases with both solar cycle and magnetic activity. Direct injection of ionospheric ions into the ring current has been observed in the outer plasmasphere. Several mechanisms for the direct injection of ions from the plasmasphere and ionosphere into the ring current have appeared. Estimation of ionospheric source strengths and residence times have led to an estimate of the magnetospheric densities that would result solely from an ionospheric outflow populating the magnetosphere. Estimated densities were quite reasonable even without inclusion of a solar wind source of ions. Ring current ions decay primarily via charge exchange with the hydrogen geocorona, however, the roles of pitch angle diffusion and Coulomb collisions in this decay process are being clarified.

Modeling and observations of ENA by the 1SEE1 spacecraft has led to a re-affirmation of the dominant role of charge exchange in ring current decay. Ion cyclotron waves contribute to ring current decay in the dusk bulge region. The role of low frequency. (< 1 Hz) ion cyclotron waves in the plasmasphere is still unclear. Other wave modes may be responsible for the pitch angle diffusion and subsequent loss of ring current ions. Coulomb collisional energy losses from ring current O⁺ to thermal electrons are sufficient to power SAR arcs and represent an energy sink for ring current O⁺ within the plasmasphere. Coulomb collisions may be important for decay of low energy (< 10 KeV) ring current ions in the plasmasphere.