scholarly journals Types of pulsating aurora: comparison of model and EISCAT electron density observations

2022 ◽  
Vol 40 (1) ◽  
pp. 1-10
Author(s):  
Fasil Tesema ◽  
Noora Partamies ◽  
Daniel K. Whiter ◽  
Yasunobu Ogawa
Keyword(s):  
Energetic Particle ◽  
Energy Deposition ◽  
Radar System ◽  
Ion Chemistry ◽  
Satellite Measurements ◽  
Electron Densities ◽  
Incoherent Scatter ◽  
Significant Difference ◽  
Energetic Particle Precipitation ◽  
Good Agreement

Abstract. Energetic particle precipitation associated with pulsating aurora (PsA) can reach down to lower mesospheric altitudes and deplete ozone. It is well documented that pulsating aurora is a common phenomenon during substorm recovery phases. This indicates that using magnetic indices to model the chemistry induced by PsA electrons could underestimate the energy deposition in the atmosphere. Integrating satellite measurements of precipitating electrons in models is considered to be an alternative way to account for such an underestimation. One way to do this is to test and validate the existing ion chemistry models using integrated measurements from satellite and ground-based observations. By using satellite measurements, an average or typical spectrum of PsA electrons can be constructed and used as an input in models to study the effects of the energetic electrons in the atmosphere. In this study, we compare electron densities from the EISCAT (European Incoherent Scatter scientific radar system) radars with auroral ion chemistry and the energetics model by using pulsating aurora spectra derived from the Polar Operational Environmental Satellite (POES) as an energy input for the model. We found a good agreement between the model and EISCAT electron densities in the region dominated by patchy pulsating aurora. However, the magnitude of the observed electron densities suggests a significant difference in the flux of precipitating electrons for different pulsating aurora types (structures) observed.

scholarly journals Types of pulsating aurora: Comparison of model and EISCAT electron density observations

2021 ◽  
Author(s):  
Fasil Tesema ◽  
Noora Partamies ◽  
Daniel K. Whiter ◽  
Yasunobu Ogawa
Keyword(s):  
Energetic Particle ◽  
Energy Input ◽  
Energy Deposition ◽  
Common Phenomenon ◽  
Ion Chemistry ◽  
Satellite Measurements ◽  
Electron Densities ◽  
Significant Difference ◽  
Energetic Particle Precipitation ◽  
Good Agreement

Abstract. Energetic particle precipitation associated with pulsating aurora (PsA) can reach down to lower mesospheric altitude and deplete ozone. It is well documented that pulsating aurora is a common phenomenon during substorm recovery phases. This indicates that using magnetic indices to model the chemistry induced by PsA electrons could underestimate the energy deposition in the atmosphere. Integrating satellite measurements of precipitating electrons in models is considered to be an alternative way to account for such underestimation. One way to do this is to test and validate existing ion chemistry models using integrated measurements from satellite and ground-based observations. By using satellite measurements, an average/typical spectrum of PsA electrons can be constructed and used as an input in models to study the effects of the energetic electrons in the atmosphere. In this study, we compare electron densities from EISCAT radars with auroral ion chemistry and the energetics model by using pulsating aurora spectra derived from POES satellites as an energy input for the model. We found a good agreement between the model and EISCAT electron densities in the region dominated by patchy pulsating aurora. However, the magnitude of the observed electron densities suggests a significant difference in the flux of precipitating electrons for different pulsating aurora types (structures) observed.

Electron Precipitation at an Auroral Latitude – Saskatoon, L = 4.4. II. Fluxes of Precipitating Electrons

1974 ◽  
Vol 52 (19) ◽  
pp. 1879-1884 ◽  
Author(s):  
A. H. Manson ◽  
Z. M. Khan
Keyword(s):  
Ionospheric Disturbance ◽  
Differential Absorption ◽  
Satellite Measurements ◽  
Electron Densities ◽  
Characteristic Energy ◽  
Mean Values ◽  
Absorption Experiment ◽  
Ambient Electron ◽  
Auroral Latitude ◽  
Good Agreement

Measurements of ambient electron densities have been made by the differential absorption experiment, on a number of aurorally disturbed nights in 1971. The measured values of the intensity of the green line (5577 Å) emission, and of the ambient electron densities, are then compared with theoretical estimates of these two variables. An exponential energy spectrum is used in the calculation, and fluxes of precipitated electrons (> 40 keV) and values for the e folding energies (E0) thereby become available. Comparisons of mean values with satellite measurements made under similar magnetic conditions, show good agreement. Calculations are also made for two specific nights, (January 26–28, 1971). Characteristic energies are typically 5 keV during the maximum of the magnetic and photometric disturbances, and increase to values of 10–15 keV near sunrise when the ionospheric disturbance (< 90 km) is greatest. The calculation is shown to be sensitive to changes in characteristic energy of the spectrum.

scholarly journals Using scale heights derived from bottomside ionograms for modelling the IRI topside profile

2005 ◽  
Vol 2 ◽  
pp. 293-297 ◽  
Author(s):  
B. W. Reinisch ◽  
X. Huang ◽  
A. Belehaki ◽  
R. Ilma
Keyword(s):  
Signal Analysis ◽  
Electron Density Profile ◽  
Electron Content ◽  
Satellite Measurements ◽  
Total Electron ◽  
Incoherent Scatter ◽  
Low Altitude ◽  
Satellite Beacon ◽  
Layer Peak ◽  
Good Agreement

Abstract. Groundbased ionograms measure the Chapman scale height HT at the F2-layer peak that is used to construct the topside profile. After a brief review of the topside model extrapolation technique, comparisons are presented between the modeled profiles with incoherent scatter radar and satellite measurements for the mid latitude and equatorial ionosphere. The total electron content TEC, derived from measurements on satellite beacon signals, is compared with the height-integrated profiles ITEC from the ionograms. Good agreement is found with the ISR profiles and with results using the low altitude TOPEX satellite. The TEC values derived from GPS signal analysis are systematically larger than ITEC. It is suggested to use HT , routinely measured by a large number of Digisondes around the globe, for the construction of the IRI topside electron density profile.

Standardisation of von Willebrand Factor in Therapeutic Concentrates: Calibration of the 1st International Standard for von Willebrand Factor Concentrate (00/514)

2002 ◽  
Vol 88 (09) ◽  
pp. 380-386 ◽  
Author(s):  
Dawn Sands ◽  
Andrew Chang ◽  
Claudine Mazurier ◽  
Anthony Hubbard
Keyword(s):  
Von Willebrand Factor ◽  
International Study ◽  
Expert Committee ◽  
International Standard ◽  
A Value ◽  
Significant Difference ◽  
Factor Concentrate ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Good Agreement

SummaryAn international study involving 26 laboratories assayed two candidate von Willebrand Factor (VWF) concentrates (B and C) for VWF:Antigen (VWF:Ag), VWF:Ristocetin Cofactor (VWF:RCo) and VWF:Collagen binding (VWF:CB) relative to the 4th International Standard Factor VIII/VWF Plasma (4th IS Plasma) (97/586). Estimates of VWF:Ag showed good agreement between different methods, for both candidates, and the overall combined means were 11.01 IU/ml with inter-laboratory variability (GCV) of 10.9% for candidate B and 14.01 IU/ml (GCV 11.8%) for candidate C. Estimates of VWF:RCo showed no significant difference between methods for both candidates and gave overall means of 9.38 IU/ml (GCV 23.7%) for candidate B and 10.19 IU/ml (GCV 24.4%) for candidate C. Prior to the calibration of the candidates for VWF:CB it was necessary to calibrate the 4th IS Plasma relative to local frozen normal plasma pools; there was good agreement between different collagen reagents and an overall mean of 0.83 IU per ampoule (GCV 11.8%) was assigned. In contrast, estimates of VWF:CB in both candidates showed large differences between collagen reagents with inter-laboratory GCV’s of 40%. Candidate B (00/514) was established as the 1st International Standard von Willebrand Factor Concentrate by the WHO Expert Committee on Biological Standardisation in November 2001 with assigned values for VWF:Ag (11.0 IU/ampoule) and VWF:RCo (9.4 IU/ampoule). Large inter-laboratory variability of estimates precluded the assignment of a value for VWF:CB.

scholarly journals NO<sub>y</sub> production, ozone loss and changes in net radiative heating due to energetic particle precipitation in 2002–2010

2017 ◽  
Author(s):  
Miriam Sinnhuber ◽  
Uwe Berger ◽  
Bernd Funke ◽  
Holger Nieder ◽  
Thomas Reddmann ◽  
...  
Keyword(s):  
Energetic Particle ◽  
Solar Maximum ◽  
Lower Thermosphere ◽  
Solar Proton ◽  
Radiative Heating ◽  
Proton Event ◽  
Late Winter ◽  
Ozone Loss ◽  
Energetic Particle Precipitation ◽  
Ionization Rates

Abstract. We analyze the impact of energetic particle precipitation on the stratospheric nitrogen budget, ozone abundances and net radiative heating using results from three global chemistry-climate models considering solar protons and geomagnetic forcing due to auroral or radiation belt electrons. Two of the models cover the atmosphere up to the lower thermosphere, the source region of auroral NO production. Geomagnetic forcing in these models is included by prescribed ionization rates. One model reaches up to about 80 km, and geomagnetic forcing is included by applying an upper boundary condition of auroral NO mixing ratios parameterized as a function of geomagnetic activity. Despite the differences in the implementation of the particle effect, the resulting modeled NOy in the upper mesosphere agrees well between all three models, demonstrating that geomagnetic forcing is represented in a consistent way either by prescribing ionization rates or by prescribing NOy at the model top. Compared with observations of stratospheric and mesospheric NOy from the MIPAS instrument for the years 2002–2010, the model simulations reproduce the spatial pattern and temporal evolution well. However, after strong sudden stratospheric warmings, particle induced NOy is underestimated by both high-top models, and after the solar proton event in October 2003, NOy is overestimated by all three models. Model results indicate that the large solar proton event in October 2003 contributed about 1–2 Gmol (109 mol) NOy per hemisphere to the stratospheric NOy budget, while downwelling of auroral NOx from the upper mesosphere and lower thermosphere contributes up to 4 Gmol NOy. Accumulation over time leads to a constant particle-induced background of about 0.5–1 Gmol per hemisphere during solar minimum, and up to 2 Gmol per hemisphere during solar maximum. Related negative anomalies of ozone are predicted by the models nearly in every polar winter, ranging from 10–50 % during solar maximum to 2–10 % during solar minimum. Ozone loss continues throughout polar summer after strong solar proton events in the Southern hemisphere and after large sudden stratospheric warmings in the Northern hemisphere. During mid-winter, the ozone loss causes a reduction of the infrared radiative cooling, i.e., a positive change of the net radiative heating (effective warming), in agreement with analyses of geomagnetic forcing in stratospheric temperatures which show a warming in the late winter upper stratosphere. In late winter and spring, the sign of the net radiative heating change turns to negative (effective cooling). This spring-time cooling lasts well into summer and continues until the following autumn after large solar proton events in the Southern hemisphere, after sudden stratospheric warmings in the Northern hemisphere.

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