Bibliography

Survey of the Favorable Conditions for Magnetosonic Wave Excitation

The ratio of the proton ring velocity (VR) to the local Alfven speed (VA), in addition to proton ring distributions, plays a key factor in the excitation of magnetosonic waves at frequencies between the proton cyclotron frequency fcp and the lower hybrid resonance frequency fLHR in the Earth\textquoterights magnetosphere. Here we investigate whether there is a statistically significant relationship between occurrences of proton rings and magnetosonic waves both outside and inside the plasmapause using particle and wave data from Van Allen Probe-A during the time period of October 2012 to December 2015. We also perform a statistical survey of the ratio of the ring energy (ER, corresponding to VR) to the Alfven energy (EA, corresponding to VA) to determine the favorable conditions under which magnetosonic waves in each of two frequency bands (fcp < f <= 0.5 fLHR and 0.5 fLHR < f < fLHR) can be excited. The results show that the magnetosonic waves in both frequency bands occur around the postnoon (12\textendash18 magnetic local time, MLT) sector outside the plasmapause when ER is comparable to or lower than EA, and those in lower-frequency bands (fcp < f <= 0.5 fLHR) occur around the postnoon sector inside the plasmapause when ER/EA > ~9. However, there is one discrepancy between occurrences of proton rings and magnetosonic waves in low-frequency bands around the prenoon sector (6\textendash12 MLT) outside the plasmapause, which suggests either that the waves may have propagated during active time from the postnoon sector after being excited during quiet time, or they may have locally excited in the prenoon sector during active time.

Kim, Kyung-Chan; Shprits, Yuri;

Published by: Journal of Geophysical Research: Space Physics      Published on: 01/2018

YEAR: 2018     DOI: 10.1002/2017JA024865

magnetosonic equatorial noise; proton ring distribution; Van Allen Probes

Dependence of the amplitude of magnetosonic waves on the solar wind and AE index using Van Allen Probes

We present the dependence of the magnetosonic wave amplitudes both outside and inside the plasmapause on the solar wind and AE index using Van Allen Probe-A spacecraft during the time period of 1 October 2012 to 31 December 2015, based on a correlation and regression analysis. Solar wind parameters considered are the southward interplanetary magnetic field (IMF BS), solar wind number density (NSW), and bulk speed (VSW). We find that the wave amplitudes outside (inside) the plasmapause are well correlated with the preceding AE, IMF BS, and NSW with time delays, each corresponding to 2\textendash3 h (3\textendash4 h), 4\textendash5 h (3\textendash4 h), and 2\textendash3 h (8\textendash9 h), while the correlation with VSW is ambiguous both inside and outside the plasmapause. As measured by the correlation coefficient, the IMF BS is the most influential solar wind parameter that affects the dayside wave amplitudes both outside and inside the plasmapause, while NSW contributes to enhancing the duskside waves outside the plasmapause. The AE effect on wave amplitudes is comparable to that of IMF BS. More interestingly, regression with time histories of the solar wind parameters and the AE index preceding the wave measurements outside the plasmapause shows significant dependence on the IMF BS, NSW, and AE: the region of peak coefficients is changed with time delay for IMF BS and AE, while isolated peaks around duskside remain gradually decrease with time for NSW. In addition, the regression with magnetosonic waves inside the plasmapause shows high coefficients around prenoon sector with preceding IMF BS and VSW.

Kim, Kyung-Chan; Shprits, Yuri;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2017

YEAR: 2017     DOI: 10.1002/2017JA024094

magnetosonic equatorial noise; solar wind dependence; Van Allen Probes