Comparison of multiple and logistic regression analyses of relativistic electron flux enhancement at geosynchronous orbit following storms.

Many factors influence relativistic outer radiation belt electron fluxes, such as waves in the ultra low frequency (ULF) Pc5, very low frequency (VLF), and electromagnetic ion cyclotron (EMIC) frequency bands, seed electron flux, Dst disturbance levels, substorm occurrence, and solar wind inputs. In this work we compared relativistic electron flux post storm vs. pre‐storm using three methods of analysis: 1) multiple regression to predict flux values following storms, 2) multiple regression to predict the size and direction of the change in electron flux, and 3) multiple logistic regression to predict only the probability of the flux rising or falling. We determined which is the most predictive model, and which factors are most influential. We found that a linear regression predicting the difference in pre‐storm and post storm flux (Model 2) results in the highest validation correlations. The logistic regression used in Model 3 had slightly weaker predictive abilities than the other two models, but had most value in providing a prediction of the probability of the electron flux increasing after a storm. Of the variables used (ULF Pc5 and VLF waves, seed electrons, substorm activity, and EMIC waves), the most influential in the final model were ULF Pc5 waves and the seed electrons. IMF Bz, Dst, and solar wind number density, velocity, and pressure did not improve any of the models, and were deemed unnecessary for effective predictions

Probing the relationship between electromagnetic ion cyclotron waves and plasmaspheric plumes near geosynchronous orbit

Plasmaspheric plumes created during disturbed geomagnetic conditions have been suggested as a major cause of increased occurrences of electromagnetic ion cyclotron (EMIC) waves at these times. We have catalogued occurrences of strong Pc1 EMIC waves from 1996 through 2003 at three automated geophysical observatories operated by the British Antarctic Survey at auroral zone latitudes in Antarctica (L = 6.28, 7.68, and 8.07) and have compared them to the occurrence of plasmaspheric plumes in space, using simultaneous data from the Magnetospheric Plasma Analyzer on the Los Alamos National Laboratory 1990-095 spacecraft, in geosynchronous orbit at the same magnetic longitude. A superposed epoch analysis of these data was conducted for several categories of disturbed geomagnetic conditions, including magnetic storms, high-speed streams, and storm sudden commencements. We found only a weak correspondence between the occurrence of strong Pc1 waves observed on the ground and either plasmaspheric plumes or intervals of extended plasmasphere at geosynchronous orbit before, during, or after the onset of any of these categories. Strong Pc1 activity peaked near or slightly after local noon during all storm phases, consistent with equatorial observations by the Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer satellite at these L shells. The highest Pc1 occurrence probability was at or 1-2 days before storm onset and during the late recovery phase. Occurrence was lowest during the early recovery phase, consistent with the decrease in solar wind pressure often seen at this time. The peak at onset is consistent with earlier observations of waves in the outer magnetosphere stimulated by sudden impulses and magnetospheric compressions

Seasonal and diurnal dependences of Pc3 and Pc4 geomagnetic pulsation power at very high latitudes

Introduction In our studies [Chugunova et al., 2002,03,04] we found the occurrence of ULF waves in the nominal Рс3-4 band in the polar cap. About 15% of this ULF activity is constituted by quasi-monochromatic waves. Though the mechanism of these waves in the region with open field lines has not been found yet [e.g., Pilipenko et al., 2004], inthis study we try to examine statistically the seasonal and yearly variations of signals and noise in the Рс3 and Рс4range. The data of observations in Antarctica have been used, where there is practically no industrial electromagnetic interference

Response of the inner and outer magnetosphere to solar wind density fluctuations during the recovery phase of a moderate magnetic storm

We examine the geomagnetic field and space plasma disturbances developing simultaneously in the solar wind, in the inner and outer magnetosphere, and on the ground from 0730 to 2030 UT on April 11, 1997 during the recovery phase of a moderate magnetic storm. The fluctuations of the solar wind density, H-component of the geomagnetic field, and power of Pcl-2 (0.1-5 Hz) waves at middle and low latitudes evolve nearly simultaneously. These fluctuations also match very well with variations of density and flux of the magnetospheric plasma at the geosynchronous orbit, and of the geomagnetic field at the geosynchronous orbit and northern polar cap. The time delay between the occurrence of disturbances in different magnetosphere regions matches the time of fast mode propagation. These disturbances are accompanied by the generation of Pcl-2 waves at mid- and high-latitude observatories in nearly the same frequency range. A scenario of the evolution of wave phenomena in different magnetospheric domains is proposed

Statistical characteristics of the spatial distribution of Pc3-4 geomagnetic pulsations at high latitudes in the Antarctic regions

The diumal variations in the parameters of Pc3 (20–60 mHz) and Pc4 (10–19 mHz) pulsations at latitudes of the dayside cusp and polar cap have been studied using data of the magnetic stations of the trans-Antarctic meridional profile for the time interval from January to March 1997 (local summer) under weakly disturbed geomagnetic conditions (AE ≤ 250 nT). The technique for estimating pulsation parameters is based on the separation of the wave packets and noise. The diumal variations in the hourly average parameters of the wave packets in the Pc3 and Pc4 bands and noise in the Pc3-4 band (10–60 mHz)—the average number of wave packets, energy of wave packets and noise, and energy of a single wave packet—turned out to be different for the stations located deep in the polar cap (Φ ∼ 87°) and at the latitudes of the dayside polar cusp (Φ ∼ 70°) and auroral oval (Φ ∼ 66°). Several sources of pulsations caused by different channels of wave energy penetration into the magnetosphere through the dayside cusp, dayside magnetopause, and dawn flank of the magnetotail apparently exist at high latitudes

Correspondence between the ULF wave power spatial distribution and auroral oval boundaries

The world-wide spatial distribution of the wave power in the Pc5 band during magnetic storms has been compared with auroral oval boundaries. The poleward and equatorward auroral oval boundaries are estimated using either the British Antarctic Survey database containing IMAGE satellite UV observations of the aurora or the OVATION model based on the DMSP particle data. The “epicenter” of the spectral power of broadband Pc5 fluctuations during the storm growth phase is mapped inside the auroral oval. During the storm recovery phase, the spectral power of narrowband Pc5 waves, both in the dawn and dusk sectors, is mapped inside the auroral oval or around its equatorward boundary. This observational result confirms previously reported effects: the spatial/temporal variations of the Pc5 wave power in the morning/pre-noon sector are closely related to the dynamics of the auroral electrojet and magnetospheric field-aligned currents. At the same time, narrowband Pc5 waves demonstrate typical resonant features in the amplitude-phase latitudinal structure. Thus, the location of the auroral oval or its equatorward boundary is the preferred latitude for magnetospheric field-line Alfven resonator excitation. This effect is not taken into account by modern theories of ULF Pc5 waves, but it could be significant for the development of more adequate models