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1.
The characteristic and properties of ULF waves in the plasmasphere boundary layer during two very quiet periods are present.
The ULF waves were detected by Double Star TC-1 when the spacecraft passed through the plasmasphere in an outbound and inbound
trajectories, respectively. A clear association between the ULF waves and periodic variations of energetic ions fluxes was
observed. The observations showed that the wave frequency was higher inside the plasmasphere than outside. The mechanism generating
these ULF waves and possible diagnosing of the “classical plasmapause” location with the ULF wave were discussed.
Supported by the National Natural Science Foundation of China (Grant Nos. 40504017, 40636031) 相似文献
2.
Interaction between ultralow frequency (ULF) waves and charged particles plays an important role in the acceleration of particles in the Van Allen radiation belts. The strong wave-particle interaction predicts an energy-dependent observational signature of particle flux variations during different stages of the ULF wave evolution. In this paper, we find that the energetic particle data newly available from an IGSO spacecraft are quite consistent with theoretical predictions, which enables the application of a best-fit procedure to quantitatively extract key parameters of the ULF waves from the particle data. The general agreement between observations and the best-fit results validates the scenario of wave-particle drift resonance within the entire ULF life span, and provides a new technique to understand the ULF wave characteristics in the absence of electromagnetic field data. We also examine the minor differences between observations and the best-fit results, and propose that the differences may result from a longitudinal dependence of the ULF wave power to be considered in a future study. 相似文献
3.
Based on observations obtained by Cluster C1, GOES 10, 12, and Polar, the global ULF wave properties are studied during the
recovery phase of a very intense magnetic storm-Halloween storm (October 31, 2003, 21:00–23:00 UT). The results indicate that
the ULF waves’ properties observed by different satellites, such as amplitude, period, etc. show large variations. This can
be interpreted as that Field Line Resonance (FLR) might take place in the region where Cluster C1 passed. The compressional
wave of the cavity mode coupled with FLR’s shear Alfven wave and fed energy to the latter, forming a large-amplitude toroidal
mode. From the point of period, Cluster C1 observed the shortest period, GOES 10, 12 observed the middle, while Polar observed
the longest. The wave period of toroidal mode observed by Cluster C1 kept almost unchanging when Cluster C1 passed L range from 11.7 to 5.3. Using the Squared Wavelet Coherence analysis method, we estimated that the FLR region in the dayside
magnetosphere could expand to at least 4 local time widths. The toroidal mode observed by Polar was a standing wave, while
the poloidal mode was a propagating wave, the observation results could be well explained by the waveguide mode theory. Since
the solarwind speed V
x was −800 km/s and the dynamic pressure varied little, we speculated that the source of the ULF wave was the Kelvin-Helmholtz
instability at the magnetopause triggered by high speed solarwind.
Supported by the National Natural Science Foundation of China(Grant Nos. 40425004, 40528005, 40390152) and the National Basic
Research Program of China (Grant No. 2006CB806305) 相似文献
4.
During the interval 06:14–07:30 UT on August 24, 2005, since the Earth’s magnetopause was suddenly compressed by the persistent
high-speed solar wind stream with the southward component of the interplanetary magnetic field (IMF), the magnetopause moved
inward for about 3.1 R E. Meanwhile, TC-1 satellite shifted from northern plasma sheet to the northern lobe/mantle region, although it kept inward
flying during the interval 06:00–07:30UT. The shift of TC-1 from the plasma sheet to the lobe/mantle is caused by the simultaneous
inward displacements of the plasma sheet and near-Earth lobe/mantle region, and their inward movement velocity is larger than
the inward motion velocity of TC-1. The joint inward displacements of the magnetopause, the lobe/mantle region and the plasma
sheet indicate that the whole magnetosphere shrinks inward due to the magnetospheric compression by the high-speed solar wind
stream, and the magnetospheric ions are attached to the magnetic field lines (i.e. ‘frozen’ in magnetic field) and move inward
in the shrinking process of magnetosphere. The large shrinkage of magnetosphere indicates that the near-Earth magnetotail
compression caused by the strong solar wind dynamic pressure is much larger than its thickening caused by the southward component
of the IMF, and the locations of magnetospheric regions with different plasmas vary remarkably with the variation of the solar
wind dynamic pressure.
Supported by the National Natural Science Foundation of China (Grant Nos. 40604018, 40523006), CSSAR (Grant No. O72114AA4S),
Scientific Research Start-up Foundation for President Prize of CAS, 973 Program of China (Grant No. 2006CB806305) and the
Specialized Research Fund for State Key Laboratories 相似文献
5.
With coordinated observations of the NOAA 15 satellite and OUL magnetometer station in Finland, we report that the electromagnetic ion cyclotron(EMIC) waves which were stimulated by the compression of the magnetosphere drive relativistic electron precipitation in geoquiescence on 1 Jan 2007. After an enhancement of solar wind dynamic pressure(SWDP), a dayside Pc1 pulsation was observed by the OUL station. Such a Pc1 pulsation is caused by an EMIC wave which propagates from the generation source to lower altitudes. Simultaneously, the NOAA 15 satellite registered an enhancement of precipitating electron count rates with energies 3 Me V within the anisotropic zone of protons. This phenomenon is coincident with the quasi-linear theoretical calculation presented in this paper. Our observations suggest that after a positive impulse of solar wind, the compression-related EMIC waves can drive relativistic electrons precipitation and play a pivotal role in the dynamic of radiation belts. 相似文献
6.
An event of Cluster-Double Star conjunction observations of magnetic reconnection at high latitude magnetopause nightside
of both cusps and solar wind transport into magnetosphere caused by such reconnection process has been investigated. During
northward IMF, Cluster/SC1 observed accelerated flows and ion heating associated with magnetic reconnection at high latitude
magnetopause nightside of southern cusp. And Double Star observed cold dense solar wind plasma transported into dayside magnetosphere.
The analysis on such conjunction observations shows that: (1) during northward IMF, magnetic reconnection occurs at high latitude
nightside of southern cusp, accompanied by accelerated flows that are observed by Cluster/SC1; (2) the direction of the accelerated
flows, with its sunward component V
x
, dawnward component V
y
, northward component V
z
, is quite consistent with the theoretical anticipation under the condition of northward IMF with dawnward component B
y
; (3) reconnection can heat plasma more in parallel direction than in perpendicular direction, to a level of about 4 keV;
(4) with reconnection taking place at high latitude magnetopause nightside of the southern cusp, TC-1 observed cold and dense
plasma transported into magnetosphere; (5) by reconnection at high latitude magnetopause nightside of both cusps, solar wind
flux tube can be captured by magnetosphere and pulled into dayside magnetosphere. This event presents further observational
evidence for magnetic reconnection at high latitude magnetopause nightside of both cusps as an important mechanism of solar
wind transport into magnetosphere.
Supported by the Ministry of Science and Technology of China (Grant No. 2006CB806305), the National Natural Science Foundation
of China (Grant Nos. 40621003, 40674094), and the Hundred Talents Program of the CAS 相似文献
7.
The equatorial and polar satellites of the Double Star Project (DSP) were launched successfully on December 29, 2003 and July
25, 2004, respectively, and both of them are operating smoothly. The DSP provides a good opportunity for investigating the
structure of the magnetosphere. Based on the DSP data collected during 2004, we have surveyed the distribution of the magnetic
fields and plasmas in the magnetosphere. It is found that: (1) Near the Earth’s equatorial plane within geocentric distances
of less than 7 R E, the Earth’s magnetic field is dipolar. In the vicinity of the magnetopause, the magnetic field is enhanced by a factor of
about 1.5, and on the nightside, the magnetic field can vary significantly from the Earth’s dipole field, likely caused by
the presence of the near-Earth tail current sheet. (2) In the day-side magnetosheath, the electron and ion densities are usually
both in the range of 10–30 cm −3; the ion and electron temperatures are usually about 200 and 50 eV, respectively. The flow pattern is usually smooth, with
a low velocity in the subsolar region and with significantly higher velocities in the dawn and dusk flanks. (3) In the region
between the magnetopause and plasmasphere the density is low, approximately 0.5–5 cm −3, and the temperature is high, about 1–10 keV for ions and 0.1–5 keV for electrons. The ion temperature has an apparent anisotropy,
with the ratio of the perpendicular and parallel temperatures being about 1.0–1.3 for the night-and dusk-side magnetosphere
and about 1.3–2.0 for the day-and dawn-side magnetosphere. There is an evident sunward convection of about 50 km/s in the
magnetosphere. On the dawn side, the flow becomes somewhat turbulent, and in the vicinity of the night-noon meridian plane,
the convection is rather slow. (4) The high-energy electrons with energies higher than 2 MeV are mainly located in the regions
with 3 < L < 4.5; the size of the high-energy electrons area varies with time, it may expand and shrink occasionally according to different
solar wind conditions and magnetic activities.
Supported by the National Natural Science Foundation of China (Grant Nos. 40621003, 40728005, 40674094, and 40390150), Ministry
of Science and Technology of China (Grant No. 2006CB806305), and Hundred Talents Program of the CAS 相似文献
8.
In recent years remarkable advances have been made in the development of physics based models of various parts of the solar-terrestrial
system (see JASTP special issues, October, November 2004; February 2007). In this paper, we focus our discussions in a specific
region of the Sun to the Earth’s environment (i.e. 1 AU). It is well-known that geomagnetic storms are caused by solar eruptions.
The consequences of these storms include particle acceleration, solar wind impact on the Earth’s magnetosphere and ionosphere,
UV-EUV radiation effects on the lower atmosphere, etc. One of the main challenges is to predict the arrival time at 1 AU of
the solar disturbance. The prospects look good for an accurate, real-time forecast scheme built on the acquisition of solar,
heliosphere and the near-Earth data and large-scale models. However, the accuracy of these models still needs improvement.
We will discuss the present status of the models and challenges to improve the simulation models.
STW and AHW are supported by AFOSR (Grant No. FA9550-07-1-0468), AURA Sub-Award C10569A of NSO’s Cooperative Agreement AST
0132798, and NSF (Grant No. ATM-0754378); CCW is supported by NASA grant NNX07AH85G, FENG is supported by National Natural
Science Foundation of China (Grant Nos. 40536029, 40621003, 40374056 and 40574058) 相似文献
9.
By analyzing hot ion and electron parameters together with magnetic field measurements from Cluster, an event of magnetopause crossing of the spacecraft has been investigated. At the latitude of about 40° and magnetic local time (MLT) of 13:20 during the southward interplanetary magnetic field (IMF), a transition layer was observed, with the magnetospheric field configuration and cold dense plasma features of the magnetosheath. The particle energy-time spectrograms inside the layer were similar to but still... 相似文献
10.
In this paper, we study the characteristic of large-scale convection electric field in the inner magnetosphere, using magnetospheric multiscale (MMS) observations between L=5 and L=8 over the period from September 1, 2015 to October 31, 2016, covering almost all magnetic local time (MLT). Observations show that the DC convection electric field generally has small variations in this region. We investigate whether the convection electric field is correlated with geomagnetic indices and solar wind parameters. It is found that, among the studied parameters, solar wind electric field, z component of interplanetary magnetic field, AE and Kp indices show good correlations with the averaged convection electric field. The results in this paper provide valuable information for understanding the role of electric field on the dynamics of the inner magnetosphere. 相似文献
11.
The rapid change in the Earth’s magnetosphere caused by solar wind disturbances has been an important part of the solar wind-magnetosphere interaction.However most of the previous studies focused on the perturbation of the Earth’s magnetic field caused by solar wind dynamic pressure changes.In this paper,we studied the response of geosynchronous magnetic field and the magnetic field to the rapid southward turning of interplanetary magnetic field during the interval 1350 1420 UT on 7May 2007.During this event,BZ component of the interplanetary magnetic field decreased from 15 nT to 10 nT within 3 min(1403 1406 UT).The geosynchronous magnetic field measured by three geosynchronous satellites(GOES 10 12)first increased and then decreased.The variations of magnetic field strength in the morning sector(9 10 LT)were much larger than those in the dawn sector(5 LT).Meanwhile,the H components of geomagnetic field on the ground have similar response features but exhibit latitude and LT dependent variations.Compared with H components,the D components do not have regular variations.Although the solar wind dynamical pressure encounters small variations,the magnetic field both in space and on the ground does not display similar variations.Therefore,the increase of geomagnetic field in the dawn sector is caused by the southward turning of IMF(interplanetary magnetic field)BZ.These results will help to better understand the coupling process of geomagnetic filed and interplanetary magnetic field. 相似文献
12.
Science China Technological Sciences - Previous studies have shown that EMIC waves occur preferentially in the afternoon sector of the magnetosphere. Here we report obliquely propagating H+ and He+... 相似文献
13.
The magnetic reconnection of magnetosphere and the magnetospheric space storms (including magnetospheric substorm, magnetic
storm, magnetospheric particle storm) has long been one of the most challenging subjects in the solar-terrestrial physics.
The reconnection mechanism and global triggering process of the magnetospheric space storms are still unclear up to now. Based
on the Double Star Program (DSP) and Cluster joint measurements, we have observed the solar wind density hole, the component
magnetic field reconnection in the magnetopause, the structures of magnetic storm ring current, global and multi-scale driven
and triggering processes of magnetospheric substorm. In this paper we will briefly introduce these results. 相似文献
15.
On January 21, 2015, a sharp increase of the solar wind dynamic pressure impacted the magnetosphere. The magnetopause moved inward to the region L 8 without causing a geomagnetic storm. The flux of the relativistic electrons in the outer radiation belt decreased by half during this event based on the observations of the particle radiation monitor(PRM) of the fourth of the China-Brazil Earth Resource Satellites(CBERS-4). The flux remained low for approximately 11 d; it did not recover after a small magnetic storm on January 26 but after a small magnetic storm on February 2. The loss and recovery of the relativistic electrons during this event are investigated using the PRM data, medium-and high-energy electron observations of NOAA-15 and the Van Allen Probes, medium-energy electron observations of GOES-13, and wave observations of the Van Allen Probes. This study shows that the loss of energetic electrons in this event is related to magnetospheric compression. The chorus waves accelerate the medium-energy electrons, which causes the recovery of relativistic electrons. The Van Allen Probes detected strong chorus waves in the region L =3–6 from January 21 to February 2. However, the flux of medium-energy electrons was low in the region. This implies that the long-lasting lack of recovery of the relativistic electrons after this event is due to the lack of the medium-energy"seed" electrons. The medium-energy electrons in the outer radiation belt may be a clue to predict the recovery of relativistic electrons. 相似文献
16.
Electromagnetic ion cyclotron (EMIC) emission is an efficient mechanism for scattering loss of energetic protons. Here, we report an event that provides both in-situ observation of energetic proton differential fluxes in the inner magnetosphere and precipitation of protons at ionospheric altitudes. During the 7–8 September 2015 geomagnetic storm the Van Allen Probes observed strong EMIC waves around L = 5 and a distinct decrement in fluxes of tens of keV protons around pitch angles 0°–45°. Meanwhile, precipitating protons at ionospheric altitudes were found to significantly enhanced (by several orders of magnitude), measured by NOAA 18 and 19 when they magnetically linked to the Van Allen Probe-A. By solving the Fokker-Planck diffusion equation, we show that EMIC waves can efficiently produce loss of energetic protons within about 2 h in the pitch angle range of ∼ 0°–45°, comparable to the satellite observations. 相似文献
18.
Quasi-periodic pulsations (QPPs) are very common oscillation features during solar flares, which have been observed in almost the entire wavelengths. However, the flare-related QPPs with double periods in the Lyα emission, particularly within a period ratio of about 2, were rarely detected. In this paper, we report the QPPs with double periods in the full-disk Lyα emission during the impulsive phase of four solar flares, i.e., SOL2016-Feb-12, SOL2014-Oct-24, SOL2014-Jun-10, and SOL2012-Nov-21. The full-disk Lyα fluxes were recorded by the extreme-ultraviolet sensor on board the Geostationary Operational Environmental Satellite. Then, the quasi-periods are estimated by the Markov chain Monte Carlo (MCMC) sampling techniques. Finally, the double periods of around 3 and 1.5 min are detected in Lyα emissions, and their period ratio is roughly equal to 2. The 3-min QPP could also be detected in the local light curves measured by the Atmospheric Imaging Assembly at wavelengths of 304 and 1600 Å. Our observations suggest that the double periodic QPPs could be regarded as the fundamental and harmonic modes of acoustic waves, which should be helpful to understand magnetohydrodynamic waves in the solar chromosphere. However, we cannot rule out that the double periods are each caused by a different generation mechanism. 相似文献
19.
Aiming at two intense shock events on October 28 and 29, 2003, this paper presents a two-step method, which combines synoptic analysis of space weather ——“observing” and quantitative prediction ——“palpating”, and then uses it to test predictions. In the first step of “observing”, on the basis of observations of the solar source surface magnetic field, interplanetary scintillation (IPS) and ACE spacecraft, we find that the propagation of the shocks is asymmetric relative to the normal direction of their solar sources, and the Earth is located near the direction of the fastest speed and the greatest energy of the shocks. As the two fast ejection shock events, the fast explosion of coronal mass of the extremely high temperature, the strong magnetic field, and the high speed background solar wind are also helpful to their rapid propagation. In the second step of “palpating”, we adopt a new membership function of the fast shock events for the ISF method. The predicted results show that for the onset time of the geomagnetic disturbance, the relative errors between the observational and the predicted results are 1.8% and 6.7%; and for the magnetic disturbance magnitude, the relative errors are 4.1% and 3.1%, re- spectively. Furthermore, the comparison among the predicted results of our two-step method with those of five other prevailing methods shows that the two-step method is advantageous. The results tell us that understanding the physical features of shock propagation thoroughly is of great importance in improving the prediction precision. 相似文献
20.
Using the data of LFEW/TC-2, we studied the dawn side chorus around substorm onsets during a strong geomagnetic storm in November
2004. During this storm, LFEW/TC-2 observed 14 dawnside chorus events. Nine of them were associated with substorms and occurred
within 40 min around the substorm onsets. The frequencies of waves have a very good correlation with the half equatorial electron
cyclotron frequencies. Chorus can be excited in the region near magnetic equatorial plane and then propagate to the mid and
high latitudes. When the wave frequencies reach the local lower hybrid frequencies, chorus can be reflected due to the lower
hybrid resonance. The time delay between the chorus and its echo is about 28 min. Previous observations show that the chorus
can propagate at most to the magnetic latitudes of 40°. LFEW/ TC-2 found for the first time that the chorus in space could
propagate to the magnetic latitude of 70°. Since most of the previous chorus observations are made close to the magnetic equatorial
plane, our results are important for the studies of excitation and propagation of whistler mode wave, and relevant relativistic
electron acceleration in the magnetosphere.
Supported by the National Natural Science Foundation of China (Grant Nos. 40621003, 40523006, 40704028, 40604018), 973 Program
of China (Grant No. 2006CB806305), and the Specialized Research Fund for State Key Laboratories of China. 相似文献
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