scholarly journals Pathways of F region thermospheric mass density enhancement via soft electron precipitation

2015 ◽  
Vol 120 (7) ◽  
pp. 5824-5831 ◽  
Author(s):  
B. Zhang ◽  
R. H. Varney ◽  
W. Lotko ◽  
O. J. Brambles ◽  
W. Wang ◽  
...  
Keyword(s):  
Mass Density ◽  
Electron Precipitation ◽  
F Region ◽  
Density Enhancement

scholarly journals Auroral ion outflow: low altitude energization

2007 ◽  
Vol 25 (9) ◽  
pp. 1967-1977 ◽  
Author(s):  
K. A. Lynch ◽  
J. L. Semeter ◽  
M. Zettergren ◽  
P. Kintner ◽  
R. Arnoldy ◽  
...  
Keyword(s):  
Electron Temperature ◽  
Scale Height ◽  
Electron Precipitation ◽  
Sounding Rocket ◽  
Time Varying ◽  
Ion Outflow ◽  
F Region ◽  
Low Energies ◽  
Moderate Energy ◽  
Low Altitude

Abstract. The SIERRA nightside auroral sounding rocket made observations of the origins of ion upflow, at topside F-region altitudes (below 700 km), comparatively large topside plasma densities (above 20 000/cc), and low energies (10 eV). Upflowing ions with bulk velocities up to 2 km/s are seen in conjunction with the poleward edge of a nightside substorm arc. The upflow is limited within the poleward edge to a region (a) of northward convection, (b) where Alfvénic and Pedersen conductivities are well-matched, leading to good ionospheric transmission of Alfvénic power, and (c) of soft electron precipitation (below 100 eV). Models of the effect of the soft precipitation show strong increases in electron temperature, increasing the scale height and initiating ion upflow. Throughout the entire poleward edge, precipitation of moderate-energy (100s of eV) protons and oxygen is also observed. This ion precipitation is interpreted as reflection from a higher-altitude, time-varying field-aligned potential of upgoing transversely heated ion conics seeded by the low altitude upflow.

scholarly journals Time-dependent responses of the neutral mass density to magnetospheric energy inputs into the cusp region in the thermosphere: A high-resolution two-dimensional local modeling

2020 ◽  
Author(s):  
Tomokazu Oigawa ◽  
Hiroyuki Shinagawa ◽  
Satochi Taguchi
Keyword(s):  
High Resolution ◽  
Electric Fields ◽  
Mass Density ◽  
Satellite Observation ◽  
Two Dimensional ◽  
Additional Energy ◽  
Champ Satellite ◽  
Cusp Region ◽  
Energy Inputs ◽  
Density Enhancement

Abstract Remarkable enhancements of the thermospheric mass density around the 400-km altitude in the cusp region have been observed by the CHAllenging Minisatellite Payload (CHAMP) satellite. We employed a high-resolution two-dimensional local model to gain insights into the extent to which the neutral-ion drag process controls the mass density’s enhancements under the energy inputs typical of the cusp. We expressed those energy inputs by quasi-static electric fields and electron precipitation. We compared two cases and calculated the thermospheric dynamics with and without neutral-ion drags. We found that in the more realistic case containing the neutral-ion drag, the calculated mass density enhancement was 10% at most, which is dramatically smaller than the observations by the CHAMP satellite (33% on average). The results also showed that the neutral-ion drag process suppresses Joule heating and neutral mass density enhancements, as well as the chemical reaction process. The discrepancy between our modeling result and the satellite observation suggests the existence of additional energy sources, such as Alfvén waves propagating from the magnetosphere, which play an important role in the cusp’s density enhancement.

scholarly journals Tidal signatures of the thermospheric mass density and zonal wind at midlatitude: CHAMP and GRACE observations

2015 ◽  
Vol 33 (2) ◽  
pp. 185-196 ◽  
Author(s):  
C. Xiong ◽  
Y.-L. Zhou ◽  
H. Lühr ◽  
S.-Y. Ma
Keyword(s):  
Electron Density ◽  
Zonal Wind ◽  
Mass Density ◽  
Phase Variation ◽  
Atmospheric Models ◽  
F Region ◽  
Main Driver ◽  
Grace Satellites ◽  
Thermospheric Dynamics

Abstract. By using the accelerometer measurements from CHAMP and GRACE satellites, the tidal signatures of the thermospheric mass density and zonal wind at midlatitudes have been analyzed in this study. The results show that the mass density and zonal wind at southern midlatitudes are dominated by a longitudinal wave-1 pattern. The most prominent tidal components in mass density and zonal wind are the diurnal tides D0 and DW2 and the semidiurnal tides SW1 and SW3. This is consistent with the tidal signatures in the F region electron density at midlatitudes as reported by Xiong and Lühr (2014). These same tidal components are observed both in the thermospheric and ionospheric quantities, supporting a mechanism that the non-migrating tides in the upper atmosphere are excited in situ by ion–neutral interactions at midlatitudes, consistent with the modeling results of Jones Jr. et al. (2013). We regard the thermospheric dynamics as the main driver for the electron density tidal structures. An example is the in-phase variation of D0 between electron density and mass density in both hemispheres. Further research including coupled atmospheric models is probably needed for explaining the similarities and differences between thermospheric and ionospheric tidal signals at midlatitudes.

scholarly journals Storm-time related mass density anomalies in the polar cap as observed by CHAMP

2010 ◽  
Vol 28 (1) ◽  
pp. 165-180 ◽  
Author(s):  
R. Liu ◽  
H. Lühr ◽  
S.-Y. Ma
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Storms ◽  
Mass Density ◽  
Small Scale ◽  
Polar Cap ◽  
Ion Outflow ◽  
The North ◽  
Scale Field ◽  
Density Enhancement ◽  
The Magnetic Field

Abstract. Strong and localized thermospheric mass density events are observed in the polar cap region by the CHAMP satellites at about 400 km altitude during geomagnetic storms. During the 4 years considered (2002–2005) 29 storms with Dst<−100 nT occurred, in 90% of them polar cap density anomalies were detected. Based on the altogether 56 anomaly events a statistical analysis was performed. The anomalies are of medium scale (500–1500 km) and seem to have a short dwell-time (<1.5 h) in the polar cap. The relative density enhancement is found to range around 2 in both hemispheres. The peak density is in the Northern Hemisphere by a factor of 1.4 larger than in the southern. Also the number of detected events in the north is twice as large as that in the south (37 vs. 19). Mass density anomalies in the polar cap occur under all interplanetary magnetic field (IMF) directions. Numerous strong anomalies have been detected in positive and negative IMF Bz conditions when the magnetic field strength is above 5 nT. Rather few events occurred for small |Bz| (<5 nT) or for positive Bz combined with vanishing By. Some of the density anomalies are accompanied by intensive small-scale field-aligned currents (FACs). But about as many show no relation to FACs. If FACs are present there, the current density is believed to be correlated with the strength of the IMF Bz. Although this paper concentrates on the presentation of the observations, we show for one event that the ion outflow mechanism could be responsible for the mass density anomalies in the polar cap.

Ionospheric density enhancement during relativistic electron precipitation

1980 ◽  
Vol 7 (11) ◽  
pp. 929-932 ◽  
Author(s):  
J. C. Foster ◽  
J. R. Doupnik ◽  
G. S. Stiles
Keyword(s):  
Relativistic Electron ◽  
Electron Precipitation ◽  
Density Enhancement

Effects of frictional ion heating and soft-electron precipitation on high-latitude F-region upflows

1995 ◽  
Vol 22 (20) ◽  
pp. 2713-2716 ◽  
Author(s):  
Chao Liu ◽  
J. L. Horwitz ◽  
P. G. Richards
Keyword(s):  
High Latitude ◽  
Electron Precipitation ◽  
Ion Heating ◽  
F Region

Large scale thermospheric density enhancements in relation to downward Poynting fluxes: Statistics from CHAMP, AMPERE and SuperDARN

2021 ◽  
Author(s):  
Daniel Billett ◽  
Gareth Perry ◽  
Lasse Clausen ◽  
William Archer ◽  
Kathryn McWilliams ◽  
...  
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Mass Density ◽  
Global Scale ◽  
Champ Satellite ◽  
Poynting Flux ◽  
Cusp Region ◽  
F Region ◽  
Primary Driver ◽  
Density Perturbations

&lt;p&gt;Large thermospheric neutral density enhancements in the cusp region have been examined for many years. The CHAMP satellite for example has enabled many observations of the perturbation, showing that it is mesoscale in size and exists on statistical timescales. Further studies examining the relationship with magnetospheric energy input have shown that fine-scale Poynting fluxes are associated with the density perturbations on a case-by-case basis, whilst others have found that mesoscale downward fluxes also exist in the cusp region statistically.&lt;/p&gt;&lt;p&gt;In this study, we use nearly 8 years of the overlapping SuperDARN and AMPERE datasets to generate global-scale patterns of the high-latitude and height-integrated Poynting flux into the ionosphere, with a time resolution of two minutes. From these, average patterns are generated based on the IMF orientation. We show the cusp is indeed an important feature in the Poynting flux maps, but the magnitude does not correlate well with statistical neutral mass density perturbations observed by the CHAMP satellite on similar spatial scales. Mesoscale height-integrated Poynting fluxes thus cannot fully account for the cusp neutral mass density enhancement, meaning energy deposition in the F-region or on fine-scales, which is not captured by our analysis, could be the primary driver.&lt;/p&gt;

Low energy electron precipitation and the ionospheric F-region in and north of the auroral zone

1972 ◽  
Vol 20 (2) ◽  
pp. 233-251 ◽  
Author(s):  
D.S. Evans ◽  
T. Jacobsen ◽  
B.N. Maehlum ◽  
G. Skovli ◽  
T. Wedde
Keyword(s):  
Auroral Zone ◽  
Low Energy ◽  
Energy Electron ◽  
Electron Precipitation ◽  
F Region ◽  
Low Energy Electron

scholarly journals Enhancement of thermospheric mass density by soft electron precipitation

2012 ◽  
Vol 39 (20) ◽  
Author(s):  
B. Zhang ◽  
W. Lotko ◽  
O. Brambles ◽  
M. Wiltberger ◽  
W. Wang ◽  
...  
Keyword(s):  
Mass Density ◽  
Electron Precipitation

Mass Determination by Direct Measurement of Electron Scattering

1975 ◽  
Vol 33 ◽  
pp. 240-241
Author(s):  
M. K. Lamvik ◽  
A. V. Crewe
Keyword(s):  
Cross Section ◽  
Electron Scattering ◽  
Mass Density ◽  
Variable Mass ◽  
Scattering Cross Section ◽  
Mass Determination ◽  
Number Density ◽  
Cross Sectional ◽  
Thin Slice ◽  
Scattering Cross

If a molecule or atom of material has molecular weight A, the number density of such units is given by n=Nρ/A, where N is Avogadro's number and ρ is the mass density of the material. The amount of scattering from each unit can be written by assigning an imaginary cross-sectional area σ to each unit. If the current I0 is incident on a thin slice of material of thickness z and the current I remains unscattered, then the scattering cross-section σ is defined by I=IOnσz. For a specimen that is not thin, the definition must be applied to each imaginary thin slice and the result I/I0 =exp(-nσz) is obtained by integrating over the whole thickness. It is useful to separate the variable mass-thickness w=ρz from the other factors to yield I/I0 =exp(-sw), where s=Nσ/A is the scattering cross-section per unit mass.

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