Auroral ion composition during large magnetic storms

1992 ◽  
Vol 70 (7) ◽  
pp. 500-509 ◽  
Author(s):  
A. W. Yau ◽  
B. A. Whalen
Keyword(s):  
Molecular Nitrogen ◽  
Magnetic Storms ◽  
Direct Result ◽  
Mass Composition ◽  
Topside Ionosphere ◽  
Molecular Formula ◽  
Ion Composition ◽  
Dominant Component ◽  
F Region ◽  
Ion Species

Ion-composition measurements from the suprathermal mass spectrometer (SMS) on AKEBONO (EXOS-D) during large magnetic storms (minimum Dst < −50 nT) reveal substantial changes in the mass composition of the auroral ionosphere. At quiet times, H+ and O+ ions dominate the high-altitude (> 1000 km) polar (Λ > 70°) ionosphere, and the minor-ion species (He+, N+, and O++) typically constitute about 10% of the total ion population: N+/O+ ≈ 0.05–0.1 and O++/O+ ≈ 0.1–0.2. During magnetic storms, the relative abundance of minor ions increase substantially, and N+ becomes a significant, at times dominant, component. During the main phase of large storms, the N+/O+ ratio reaches peak values of unity in the dayside. Likewise, the peak O++/O+ ratio reaches 0.4–0.5 at storm time. In addition, molecular [Formula: see text] and NO+ ions are occasionally present, and constitute ~5% of the total ion flux. The observed ions typically have energies of 5–20 eV/q, and are moving upward along the field line. They are believed to originate from the topside ionosphere. The increased abundance of N+ ions during large magnetic storms is believed to be a direct result of the increase in molecular nitrogen density in the F-region and topside ionosphere due to thermospheric heating in the presence of prolonged auroral activity. This implies that N+ ions may possibly be the dominant plasma component in the magnetosphere during very large magnetic storms.

scholarly journals WN4 effect on longitudinal distribution of different ion species in the topside ionosphere at low latitudes by means of DEMETER, DMSP-F13 and DMSP-F15 data

2009 ◽  
Vol 27 (7) ◽  
pp. 2893-2902 ◽  
Author(s):  
L. Bankov ◽  
R. Heelis ◽  
M. Parrot ◽  
J.-J. Berthelier ◽  
P. Marinov ◽  
...  
Keyword(s):  
Density Distribution ◽  
Major Ions ◽  
Local Times ◽  
Longitudinal Distribution ◽  
Topside Ionosphere ◽  
Regular Feature ◽  
Ion Density ◽  
F Region ◽  
Longitudinal Variations ◽  
Ion Species

Abstract. Plasma probe data from DMSP-F13, DMSP-F15 and DEMETER satellites were used to examine longitudinal structures in the topside equatorial ionosphere during fall equinox conditions of 2004 year. Since the launch of DEMETER satellite on 29 June 2004, all these satellites operate close together in the topside ionosphere. Here, data taken from Special Sensor-Ion, Electron and Scintillations (SSIES) instruments on board DMSP-F13, F15 and Instrument Analyser de Plasma (IAP) on DEMETER, are used. Longitudinal variations in the major ions at two altitudes (~730 km for DEMETER and ~840 km for DMSP) are studied to further describe the recently observed "wavenumber-four" (WN4) structures in the equatorial topside ionosphere. Different ion species H+, He+ and O+ have a rather complex longitudinal behavior. It is shown that WN4 is almost a regular feature in O+ the density distribution over all local times covered by these satellites. In the evening local time sector, H+ ions follow the O+ behavior within WN4 structures up to the pre-midnight hours. Near sunrise H+ and later in the daytime, He+ longitudinal variations are out of phase with respect to O+ ions and effectively reduce the effect of WN4 on total ion density distribution at altitudes 730–840 km. It is shown that both a WN4 E×B drift driver and local F-region winds must be considered to explain the observed ion composition variations.

scholarly journals Self-consistent modelling of the daytime electron density profile in the ionospheric F region

1997 ◽  
Vol 15 (3) ◽  
pp. 314-326 ◽  
Author(s):  
A. Mikhailov ◽  
K. Schlegel
Keyword(s):  
Electron Density ◽  
Molecular Nitrogen ◽  
Molecular Ions ◽  
Ion Composition ◽  
Ion Temperature ◽  
Incoherent Scatter ◽  
Plasma Drift ◽  
F Region ◽  
Self Consistent ◽  
Exospheric Temperature

Abstract. A theoretical self-consistent method for the description of daytime Ne(h) profiles in the ionospheric F region measured by EISCAT is proposed. It is based on the use of a theoretical F-region model and measured electron density, Ne(h), electron, Te(h), and ion temperature, Ti(h), and field-aligned plasma drift Vl(h) profiles. The method describes the observed Ne(h) profile with high accuracy for quiet and disturbed conditions. Two versions of the method are considered: in the first the exospheric temperature Tex is derived from a procedure minimizing [log(Ne(h)obs / Ne(h)cal]2, in the second Tex is deduced from the ion energy conservation in the F region. The method allows us to infer from the incoherent-scatter observations: concentrations of atomic oxygen, [O], molecular oxygen, [O2], molecular nitrogen, [N2] the vertical plasma drift, W, the exospheric temperature. Tex, and the shape parameter S in the neutral temperature profile. The ratio ([O+]/Ne) calculated by the theoretical model is used to correct Te(h), Ti(h) and Ne(h) profiles routinely measured with EISCAT which are known to depend strongly on the actual applied ion-composition model. Such a correction is especially important for geomagnetically disturbed periods when the F region is strongly enriched with molecular ions. We conclude that four of the six thermospheric parameters, namely [O], [N2], W and Tex can be confidently inferred from the EISCAT observations, while the other two derived parameters, [O2] ans S are less reliable. The method can be used for the analysis of long-term (seasonal, solar cycle) as well as for day-to-day variations of the thermospheric parameters and the F-region ion composition using daytime incoherent-scatter observations.

scholarly journals Observations of diverging field-aligned ion flow with the ESR

2004 ◽  
Vol 22 (3) ◽  
pp. 889-899 ◽  
Author(s):  
S. C. Buchert ◽  
Y. Ogawa ◽  
R. Fujii ◽  
A. P. van Eyken
Keyword(s):  
Field Line ◽  
Geomagnetic Field ◽  
Plasma Temperature ◽  
Ionization Mechanism ◽  
Soft Particle ◽  
Polar Ionosphere ◽  
Ion Composition ◽  
Ion Flow ◽  
F Region ◽  
Ionization Balance

Abstract. We report on observations of a diverging ion flow along the geomagnetic field that is often seen at the EISCAT Svalbard radar. The flow is upward above the peak of the electron density in the F-region and downward below the peak. We estimate that in such events mass transport along the field line is important for the ionization balance, and that the shape of the F-layer and its ion composition should be strongly influenced by it. Diverging flow typically occurs when there are signatures of direct entry of sheath plasma to the ionosphere in the form of intense soft particle precipitation, and we suggest that it is caused by the ionization and ionospheric electron heating associated with this precipitation. On average, 30% of all events with ion upflow also show significant ion downflow below. Key words.Ionosphere (polar ionosphere; ionization mechanism; plasma temperature and density)

scholarly journals He<sup>+</sup> dominance in the plasmasphere during geomagnetically disturbed periods: 1. Observational results

2002 ◽  
Vol 20 (4) ◽  
pp. 461-470 ◽  
Author(s):  
M. H. Denton ◽  
G. J. Bailey ◽  
C. R. Wilford ◽  
A. S. Rodger ◽  
S. Venkatraman
Keyword(s):  
Geomagnetic Storm ◽  
Plasma Temperature ◽  
Recovery Phase ◽  
Geomagnetic Disturbance ◽  
Topside Ionosphere ◽  
Exchange Reactions ◽  
Geomagnetic Disturbances ◽  
Model Calculations ◽  
Flux Tubes ◽  
F Region

Abstract. Observations made by the DMSP F10 satellite during the recovery phase from geomagnetic disturbances in June 1991 show regions of He+ dominance around 830 km altitude at 09:00 MLT. These regions are co-located with a trough in ionisation observed around 55° in the winter hemisphere. Plasma temperature and concentration observations made during the severe geomagnetic storm of 24 March 1991 are used as a case study to determine the effects of geomagnetic disturbances along the orbit of the F10 satellite. Previous explanations for He+ dominance in this trough region relate to the part of the respective flux tubes that is in darkness. Such conditions are not relevant for this study, since the whole of the respective flux tubes are sunlit. A new mechanism is proposed to explain the He+ dominance in the trough region. This mechanism is based on plasma transport and chemical reaction effects in the F-region and topside ionosphere, and on the time scales for such chemical reactions. Flux tubes previously depleted by geomagnetic storm effects refill during the recovery phase from the ionosphere as a result of pressure differences along the flux tubes. Following a geomagnetic disturbance, the He+ ion recovers quickly via the rapid photoionisation of neutral helium, in the F-region and the topside. The recovery of the O+ and H+ ions is less rapid. This is proposed as a result of the respective charge exchange reactions with neutral atomic hydrogen and oxygen. Preliminary model calculations support the proposed mechanism.Key words. Magnetospheric physics (storms and sub-storms, plasmasphere)

scholarly journals F-region electron density and <i>T<sub>e</sub> / T<sub>i</sub></i> measurements using incoherent scatter power data collected at ALTAIR

2006 ◽  
Vol 24 (5) ◽  
pp. 1333-1342 ◽  
Author(s):  
M. Milla ◽  
E. Kudeki
Keyword(s):  
Electron Density ◽  
Topside Ionosphere ◽  
Low Latitude ◽  
Aspect Angle ◽  
Incoherent Scatter ◽  
F Region ◽  
Regularized Inversion ◽  
The Pacific ◽  
Resolution Electron ◽  
Low Latitude Ionosphere

Abstract. The ALTAIR UHF radar was used in an incoherent scatter experiment to observe the low-latitude ionosphere during the Equis 2 rocket campaign. The measurements provided the first high-resolution electron density maps of the low-latitude D- and E-region in the Pacific sector and also extended into the F-region and topside ionosphere. Although the sampling frequency was well below the Nyquist frequency of F-region returns, we were able to estimate Te / Ti ratio and infer unbiased electron density estimates using a regularized inversion technique described here. The technique exploits magnetic aspect angle dependence of ISR cross-section for Te>Ti.

scholarly journals The dependence of plasma density in the topside ionosphere on the solar activity level

2007 ◽  
Vol 25 (6) ◽  
pp. 1337-1343 ◽  
Author(s):  
L. Liu ◽  
W. Wan ◽  
X. Yue ◽  
B. Zhao ◽  
B. Ning ◽  
...  
Keyword(s):  
Solar Activity ◽  
Plasma Density ◽  
Rate Of Change ◽  
Activity Level ◽  
Nonlinear Dependence ◽  
High Solar Activity ◽  
Topside Ionosphere ◽  
Ion Density ◽  
Solar Activity Level ◽  
F Region

Abstract. In this paper, the ten-year (1996–2005) total ion density Ni measurements from the Defense Meteorological Satellite Program (DMSP) spacecraft in the morning and evening (09:30 and 21:30 LT) sectors have been analyzed to explore the dependence of plasma densities in the topside ionosphere at middle and low latitudes on the solar activity level. Results indicate that there is a strong solar activity dependence of DMSP Ni at 848 km altitude, which has latitudinal and seasonal features. The plasma density in the topside ionosphere has an approximately linear dependence on daily F107 and a strongly nonlinear dependence on SEM/SOHO EUV, such that the change rate of Ni becomes greater with increasing solar EUV. This is quite different from the dependence of Ni near the F-Region peak (NmF2), at which the rate of change of NmF2 decreases with increasing solar EUV. The rate of change of Ni at the DMSP altitude is greatest in the latitude range where Ni is greatest during high solar activity. We suggest that this greater rate of change (or amplification effect) of Ni at the DMSP altitude is mainly a consequence of the solar activity variations of the topside scale height. The changes in the height of the F-Region peak (hmF2) and the density NmF2 play a secondary role.

CIR/HSSS-related TID activity and their interhemispheric circulation

2020 ◽  
Author(s):  
Dalia Buresova ◽  
John Bosco Habarulema ◽  
Jurgen Watermann ◽  
Ilya K. Edemskiy ◽  
Jaroslav Urbar ◽  
...  
Keyword(s):  
Quantitative Information ◽  
Magnetic Storms ◽  
Detection Methods ◽  
Gps Receiver ◽  
Plasma Bubbles ◽  
Plasma Drift ◽  
Space And Time ◽  
Ionospheric Variability ◽  
F Region ◽  
Gnss Receivers

&lt;p&gt;The paper presents results of the analysis of the changes in the regular ionospheric variability and TID activity observed during CIR/HSSS-related storms. We analyzed main ionospheric parameters retrieved from manually scaled ionograms, plasma drift measurements and TEC data obtained from several European and African ionospheric stations and GNSS receivers. Most of the observed storm-related TIDs had periods of 60-180 min (LSTIDs). During the analyzed storms we also observed extraordinary spreads and plasma bubbles at the F region heights. The results of the analysis were compared with the TID activity during strong magnetic storms of CME origin along the European-African sector. In order to obtain quantitative information on the likeliness and morphology of interhemispheric circulation of LSTIDs at about 40 events were examined lasting between 8 and 24 hours each. We used exclusively GPS-based detection methods, specifically information on TEC, TEC deviations in space and time from a background reference (dTEC), and the Rate of TEC change in time (ROT), all inferred from GPS receiver networks in Europe and Africa. We conclude that hemispheric conjugacy of LSTID is highly probable while interhemispheric circulation rather unlikely but still occurring during some periods.&lt;/p&gt;

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