Nighttime Pc3 pulsations: MM100 and MAGDAS observations

Nadezda V Yagova,Nataliya S Nosikova,Akimasa Yoshikawa,Vyacheslav A Pilipenko,Kiyohumi Yumoto,Jan Reda,Balazs Heilig

doi:10.1186/s40623-017-0647-x

Abstract

In this paper, we present a statistical and case analysis of nighttime Pc3 pulsations observed from middle to equatorial latitudes during the year 2003. We found two groups of nighttime Pc3 pulsations. Pc3s of the first group are in fact the nightside counterpart of morning Pc3 pulsations with large azimuthal scales slowly attenuating toward midnight. Such night signatures of morning Pc3 waves are observed during the periods of fast solar wind (V>500,hbox {km/s}). The second type is the locally generated night Pc3 pulsations. They can be observed under moderate solar wind velocities. Maximal occurrence rates and amplitudes for these pulsations are recorded at middle geomagnetic latitudes near the local magnetic midnight. Probably, they are associated with auroral activations or local non-substorm bursty processes.Graphical abstractAn example of a nighttime Pc3 pulsationGraphical abstractEmpirical probability density function of the solar wind speed for the intervals with the two types of night Pc3 pulsations and for all the intervals analyzed.

Highlights

Narrowband Pc3 geomagnetic pulsations in the frequency band 20–80 mHz are observed regularly at middle latitudes almost every day
The midlatitude Pc3 pulsations are commonly recorded in a wide range of magnetic local times (MLT) from early morning to late evening hours, whereas the maximal amplitudes and occurrence rates are observed in the morning/pre-noon MLT sector
The frequency of upstream waves is determined by the magnitude B IMF of the interplanetary magnetic field (IMF) (Guglielmi and Troitskaya 1974) due to their ion-cyclotron origin

Summary

Background

Narrowband Pc3 geomagnetic pulsations in the frequency band 20–80 mHz are observed regularly at middle latitudes almost every day. This correspondence naturally leads to a suggestion that night Pc3 occurrence is controlled by the solar wind speed To check this hypothesis, we selected automatically highly coherent Pc3 events recorded at BEL and KAT (same L-shell) in 2003, for which the BEL station was on the nightside, while KAT was on the day side, and when the day side amplitude was larger than the nightside one. This result is meaningful at better than 1% confidence level With these two tests, we have found that night Pc3s of day origin, selected only with amplitude and coherence criterion, demonstrate features typical for dayside Pc3s and nighttime Pc3 pulsations of intermediate and high frequencies studied in Villante and Tiberi (2016) at L = 1.6. A more precise analysis of group velocity is required

Findings

Discussion

Conclusion