scholarly journals Low altitude energetic electron lifetimes after enhanced magnetic activity as deduced from SAC-C and DEMETER data

2010 ◽  
Vol 28 (3) ◽  
pp. 849-859 ◽  
Author(s):  
S. Benck ◽  
L. Mazzino ◽  
M. Cyamukungu ◽  
J. Cabrera ◽  
V. Pierrard
Keyword(s):  
Pitch Angle ◽  
Energetic Electron ◽  
Magnetic Activity ◽  
Decay Rates ◽  
Data Sets ◽  
Quiet Time ◽  
Loss Cone ◽  
Energetic Electrons ◽  
Low Altitude ◽  
The Difference

Abstract. When flux enhancements of energetic electrons are produced as a consequence of geomagnetic storm occurrence, they tend to vanish gradually when the magnetic activity calms down and the fluxes decay to quiet-time levels. We use SAC-C and DEMETER low altitude observations to estimate the energetic electron lifetimes (E=0.16–1.4 MeV, L=1.6–5, B=0.22–0.46 G) and compare the decay rates to those observed at high altitude. While crossing the radiation belts at high latitude, the SAC-C and DEMETER instruments sample particles with small equatorial pitch angles (αeq<18° for L>2.5) whereas the comparison is done with other satellite data measured mainly in the equatorial plane (for αeq>75°). While in the inner belt and in the slot region no significant lifetime differences are observed from the data sets with different αeq, in the outer belt, for the least energetic electrons (<500 keV), the lifetimes are up to ~3 times larger for the electrons with the equatorial pitch-angle close to the loss cone than for those mirroring near the equator. The difference decreases with increasing energy and vanishes for energies of about 1 MeV.

scholarly journals Comparison between CNA and energetic electron precipitation: simultaneous observation by Poker Flat Imaging Riometer and NOAA satellite

2005 ◽  
Vol 23 (5) ◽  
pp. 1555-1563 ◽  
Author(s):  
Y.-M. Tanaka ◽  
M. Ishii ◽  
Y. Murayama ◽  
M. Kubota ◽  
H. Mori ◽  
...  
Keyword(s):  
Pitch Angle ◽  
Electron Flux ◽  
Energetic Electron ◽  
Energetic Particles ◽  
Electron Precipitation ◽  
Angle Distribution ◽  
Pitch Angle Distribution ◽  
Loss Cone ◽  
Isotropic Pitch ◽  
Trapped Electron

Abstract. The cosmic noise absorption (CNA) is compared with the precipitating electron flux for 19 events observed in the morning sector, using the high-resolution data obtained during the conjugate observations with the imaging riometer at Poker Flat Research Range (PFRR; 65.11° N, 147.42° W), Alaska, and the low-altitude satellite, NOAA 12. We estimate the CNA, using the precipitating electron flux measured by NOAA 12, based on a theoretical model assuming an isotropic pitch angle distribution, and quantitatively compare them with the observed CNA. Focusing on the eight events with a range of variation larger than 0.4dB, three events show high correlation between the observed and estimated CNA (correlation coefficient (r0)>0.7) and five events show low correlation (r0<0.5). The estimated CNA is often smaller than the observed CNA (72% of all data for 19 events), which appears to be the main reason for the low-correlation events. We examine the assumption of isotropic pitch angle distribution by using the trapped electron flux measured at 80° zenith angle. It is shown that the CNA estimated from the trapped electron flux, assuming an isotropic pitch angle distribution, is highly correlated with the observed CNA and is often overestimated (87% of all data). The underestimate (overestimate) of CNA derived from the precipitating (trapped) electron flux can be interpreted in terms of the anisotropic pitch angle distribution similar to the loss cone distribution. These results indicate that the CNA observed with the riometer may be quantitatively explained with a model based on energetic electron precipitation, provided that the pitch angle distribution and the loss cone angle of the electrons are taken into account. Keywords. Energetic particles, precipitating – Energetic particles, trapped – Ionosphere-magnetosphere interactions

scholarly journals Modeling whistler wave generation regimes in magnetospheric cyclotron maser

2004 ◽  
Vol 22 (10) ◽  
pp. 3561-3570 ◽  
Author(s):  
D. L. Pasmanik ◽  
A. G. Demekhov ◽  
V. Y. Trakhtengerts ◽  
M. Parrot
Keyword(s):  
Source Parameters ◽  
Energetic Electron ◽  
Low Frequency ◽  
Wave Generation ◽  
Whistler Wave ◽  
Particle Precipitation ◽  
Loss Cone ◽  
Energetic Electrons ◽  
Cyclotron Maser ◽  
Different Characteristics

Abstract. Numerical analysis of the model for cyclotron instability in the Earth's magnetosphere is performed. This model, based on the self-consistent set of equations of quasi-linear plasma theory, describes different regimes of wave generation and related energetic particle precipitation. As the source of free energy the injection of energetic electrons with transverse anisotropic distribution function to the interaction region is considered. A parametric study of the model is performed. The main attention is paid to the analysis of generation regimes for different characteristics of energetic electron source, such as the shape of pitch angle distributions and its intensity. Two mechanisms of removal of energetic electrons from a generation region are considered, one is due to the particle precipitation through the loss cone and another one is related to the magnetic drift of energetic particles. It was confirmed that two main regimes occur in this system in the presence of a constant particle source, in the case of precipitation losses. At small source intensity relaxation oscillations were found, whose parameters are in good agreement with simplified analytical theory developed earlier. At a larger source intensity, transition to a periodic generation occurs. In the case of drift losses the regime of self-sustained periodic generation regime is realized for source intensity higher than some threshold. The dependencies of repetition period and dynamic spectrum shape on the source parameters were studied in detail. In addition to simple periodic regimes, those with more complex spectral forms were found. In particular, alteration of spikes with different spectral shape can take place. It was also shown that quasi-stationary generation at the low-frequency band can coexist with periodic modulation at higher frequencies. On the basis of the results obtained, the model for explanation of quasi-periodic whistler wave emissions is verified.

scholarly journals Proton isotropy boundaries as measured on mid- and low-altitude satellites

2005 ◽  
Vol 23 (5) ◽  
pp. 1839-1847 ◽  
Author(s):  
N. Yu. Ganushkina ◽  
T. I. Pulkkinen ◽  
M. V. Kubyshkina ◽  
V. A. Sergeev ◽  
E. A. Lvova ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Pitch Angle ◽  
Large Field ◽  
Tail Region ◽  
Isotropic Distribution ◽  
Distribution Boundary ◽  
Magnetospheric Configuration And Dynamics ◽  
Low Altitude ◽  
The Difference

Abstract. Polar CAMMICE MICS proton pitch angle distributions with energies of 31-80 keV were analyzed to determine the locations where anisotropic pitch angle distributions (perpendicular flux dominating) change to isotropic distributions. We compared the positions of these mid-altitude isotropic distribution boundaries (IDB) for different activity conditions with low-altitude isotropic boundaries (IB) observed by NOAA 12. Although the obtained statistical properties of IDBs were quite similar to those of IBs, a small difference in latitudes, most pronounced on the nightside and dayside, was found. We selected several events during which simultaneous observations in the same local time sector were available from Polar at mid-altitudes, and NOAA or DMSP at low-altitudes. Magnetic field mapping using the Tsyganenko T01 model with the observed solar wind input parameters showed that the low- and mid-altitude isotropization boundaries were closely located, which leads us to suggest that the Polar IDB and low-altitude IBs are related. Furthermore, we introduced a procedure to control the difference between the observed and model magnetic field to reduce the large scatter in the mapping. We showed that the isotropic distribution boundary (IDB) lies in the region where Rc/ρ~6, that is at the boundary of the region where the non-adiabatic pitch angle scattering is strong enough. We therefore conclude that the scattering in the large field line curvature regions in the nightside current sheet is the main mechanism producing isotropization for the main portion of proton population in the tail current sheet. This mechanism controls the observed positions of both IB and IDB boundaries. Thus, this tail region can be probed, in its turn, with observations of these isotropy boundaries. Keywords. Magnetospheric physics (Energetic particles, Precipitating; Magnetospheric configuration and dynamics; Magnetotail)

Statistical Study of Pitch Angle Diffusion during Substorm Injections

2020 ◽  
Author(s):  
Reihaneh Ghaffari ◽  
Christopher Cully
Keyword(s):  
Pitch Angle ◽  
Energetic Electron ◽  
Loss Cone ◽  
Linear Diffusion ◽  
Whistler Mode ◽  
Wave Measurements ◽  
Whistler Mode Waves ◽  
Substorm Injection ◽  
Injection Region

&lt;p&gt;Energetic Electron Precipitation (EEP) associated with substorm injections typically occurs when magnetospheric waves, particularly whistler-mode waves, resonantly interact with electrons to affect their equatorial pitch angle. This can be considered as a diffusion process that scatters particles into the loss cone. In this study, we investigate whistler-mode wave generation in conjunction with electron injections using in-situ wave measurements by the Themis mission. We calculate the pitch angle diffusion coefficient exerted by the observed wave activity using the quasi-linear diffusion approximation and estimate scattering efficiency in the substorm injection region to constrain where and how much scattering happens typically during these events.&lt;/p&gt;

Statistical Distribution of Energetic Electron Precipitation due to Hiss Waves In the Earth’s Inner Magnetosphere

2021 ◽  
Author(s):  
Qianli Ma
Keyword(s):  
Energy Flux ◽  
Pitch Angle ◽  
Energetic Electron ◽  
Statistical Distribution ◽  
Electron Precipitation ◽  
Characteristic Energy ◽  
Loss Cone ◽  
Inner Magnetosphere ◽  
The Earth ◽  
Chorus Waves

&lt;p&gt;We investigate the statistical distribution of energetic electron precipitation from the equatorial magnetosphere due to hiss waves in the plasmasphere and plumes. Using Van Allen Probes measurements, we calculate the pitch angle diffusion coefficients at the pitch angle of bounce loss cone, and evaluate the energy spectrum of precipitating electron flux using quasi-linear theory. Our ~6.5 years survey shows that, during disturbed times, the plasmaspheric hiss mostly causes the electron precipitation at L &gt; 3 near the dayside in the plasmasphere, and hiss waves in plume cause the precipitation at L &gt; 5 near dayside and L &gt; 3.5 near the dusk side. The precipitating energy flux increases with increasing geomagnetic index, and is typically higher in the plasmaspheric plume than the plasmasphere. The characteristic energy of precipitation increases from ~20 keV at L = 6 to ~100 keV at L = 3, potentially causing the loss of electrons at several hundred keV. Although the total precipitating energy flux due to hiss waves is generally lower than the precipitation due to whistler mode chorus waves, the characteristic energy of precipitation due to hiss is higher, and the precipitation extends closer to the Earth.&lt;/p&gt;

Search for low-altitude acceleration mechanisms during an auroral substorm

1968 ◽  
Vol 46 (8) ◽  
pp. 911-921 ◽  
Author(s):  
I. B. McDiarmid ◽  
E. E. Budzinski
Keyword(s):  
Pitch Angle ◽  
Magnetic Moments ◽  
Angular Distributions ◽  
Angle Distribution ◽  
Particle Interactions ◽  
Pitch Angle Distribution ◽  
Loss Cone ◽  
Black Brant ◽  
Auroral Substorm ◽  
Low Altitude

Two Black Brant rockets were fired simultaneously from Fort Churchill during an auroral substorm. Electron spectra and angular distributions were examined at altitudes up to 800 km in an attempt to observe the effects of acceleration or loss mechanisms acting on the particles at low altitudes. In particular, the variation of the pitch-angle distribution in the loss cone for electrons with energies greater than 40 keV and near 10 keV was examined as a function of altitude. It was found that the distributions within the loss cone at higher altitudes decreased more slowly with pitch angle than expected on the basis of the observed distributions at low altitudes if no forces other than the earth's magnetic field act on the particles. The discrepancy was larger for 10-keV electrons than for 40-keV electrons. It is concluded that mechanisms exist at altitudes below 800 km which can alter the magnetic moments and/or the energies of the particles. No satisfactory explanation of the observed discrepancy has been found. An attempt was made to interpret the results in terms of wave-particle interactions which could give rise to pitch-angle diffusion, but the magnetic-wave amplitude required is at least two orders of magnitude larger than observed values.

POSTPARTUM AMENORRHOEA IN RURAL EASTERN UTTAR PRADESH, INDIA

1998 ◽  
Vol 30 (2) ◽  
pp. 227-243
Author(s):  
K. N. S. YADAVA ◽  
S. K. JAIN
Keyword(s):  
Higher Education ◽  
Uttar Pradesh ◽  
Current Status Data ◽  
North India ◽  
Current Status ◽  
Data Sets ◽  
Survival Status ◽  
The Mean ◽  
The Difference ◽  
Using Data

This paper calculates the mean duration of the postpartum amenorrhoea (PPA) and examines its demographic, and socioeconomic correlates in rural north India, using data collected through 'retrospective' (last but one child) as well as 'current status' (last child) reporting of the duration of PPA.The mean duration of PPA was higher in the current status than in the retrospective data;n the difference being statistically significant. However, for the same mothers who gave PPA information in both the data sets, the difference in mean duration of PPA was not statistically significant. The correlates were identical in both the data sets. The current status data were more complete in terms of the coverage, and perhaps less distorted by reporting errors caused by recall lapse.A positive relationship of the mean duration of PPA was found with longer breast-feeding, higher parity and age of mother at the birth of the child, and the survival status of the child. An inverse relationship was found with higher education of a woman, higher education of her husband and higher socioeconomic status of her household, these variables possibly acting as proxies for women's better nutritional status.

Statistics of pulsating auroras on the basis of all-sky TV data from five stations. I. Occurrence frequency

1981 ◽  
Vol 59 (8) ◽  
pp. 1150-1157 ◽  
Author(s):  
T. Oguti ◽  
S. Kokubun ◽  
K. Hayashi ◽  
K. Tsuruda ◽  
S. Machida ◽  
...  
Keyword(s):  
Local Time ◽  
Cold Plasma ◽  
Geomagnetic Latitude ◽  
Auroral Oval ◽  
Magnetic Activity ◽  
Occurrence Frequency ◽  
Frequency Of Occurrence ◽  
Occurrence Probability ◽  
Energetic Electrons ◽  
Plasma Irregularities

The frequency of occurrence of pulsating auroras is statistically examined on the basis of all-sky TV data for 34 nights from five stations, in a range from 61.5 to 74.3° in geomagnetic latitude. The results are that: (1) occurrence probability of a pulsating aurora is 100% after 4 h in geomagnetic local time, (2) pulsating auroras occur in the morning hours along the auroral oval even when magnetic activity is as small as 0o ≤ Kp ≤ 1, (3) pulsating auroras occur even in the evening when Kp increases to greater than 3−, (4) drift of pulsating auroras is westward in the evening while it is eastward in the morning hours, (5) the region of pulsating auroras splits into two zones, 64 to 68° and 61 to 63° in geomagnetic latitude, after 4 h geomagnetic local time for Kp from 2o to 3−, and the splitting also appears to exist for greater Kp as evidenced by observation other than our auroral data. These results are discussed in relation to distributions of cold plasma irregularities and energetic electrons in the magnetosphere.

Sign in / Sign up

Export Citation Format

Share Document