TY  - JOUR
A1  - Xiong, Chao
A1  - Stolle, Claudia
A1  - Luehr, Hermann
A1  - Park, Jaeheung
A1  - Fejer, Bela G.
A1  - Kervalishvili, Guram N.
T1  - Scale analysis of equatorial plasma irregularities derived from Swarm constellation
JF  - Earth, planets and space
N2  - In this study, we investigated the scale sizes of equatorial plasma irregularities (EPIs) using measurements from the Swarm satellites during its early mission and final constellation phases. We found that with longitudinal separation between Swarm satellites larger than 0.4 degrees, no significant correlation was found any more. This result suggests that EPI structures include plasma density scale sizes less than 44 km in the zonal direction. During the Swarm earlier mission phase, clearly better EPI correlations are obtained in the northern hemisphere, implying more fragmented irregularities in the southern hemisphere where the ambient magnetic field is low. The previously reported inverted-C shell structure of EPIs is generally confirmed by the Swarm observations in the northern hemisphere, but with various tilt angles. From the Swarm spacecrafts with zonal separations of about 150 km, we conclude that larger zonal scale sizes of irregularities exist during the early evening hours (around 1900 LT).
KW  - Equatorial plasma irregularities
KW  - Ionospheric scale lengths
KW  - Swarm constellation
Y1  - 2016
U6  - https://doi.org/10.1186/s40623-016-0502-5
SN  - 1880-5981
VL  - 68
SP  - 189
EP  - 202
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Yamazaki, Yosuke
A1  - Stolle, Claudia
A1  - Matzka, Jürgen
A1  - Siddiqui, Tarique Adnan
A1  - Luehr, Hermann
A1  - Alken, Patrick
T1  - Longitudinal Variation of the Lunar Tide in the Equatorial Electrojet
JF  - Journal of geophysical research : Space physics
N2  - The atmospheric lunar tide is one known source of ionospheric variability. The subject received renewed attention as recent studies found a link between stratospheric sudden warmings and amplified lunar tidal perturbations in the equatorial ionosphere. There is increasing evidence from ground observations that the lunar tidal influence on the ionosphere depends on longitude. We use magnetic field measurements from the CHAMP satellite during July 2000 to September 2010 and from the two Swarm satellites during November 2013 to February 2017 to determine, for the first time, the complete seasonal- longitudinal climatology of the semidiurnal lunar tidal variation in the equatorial electrojet intensity. Significant longitudinal variability is found in the amplitude of the lunar tidal variation, while the longitudinal variability in the phase is small. The amplitude peaks in the Peruvian sector (similar to 285 degrees E) during the Northern Hemisphere winter and equinoxes, and in the Brazilian sector (similar to 325 degrees E) during the Northern Hemisphere summer. There are also local amplitude maxima at similar to 55 degrees E and similar to 120 degrees E. The longitudinal variation is partly due to the modulation of ionospheric conductivities by the inhomogeneous geomagnetic field. Another possible cause of the longitudinal variability is neutral wind forcing by nonmigrating lunar tides. A tidal spectrum analysis of the semidiurnal lunar tidal variation in the equatorial electrojet reveals the dominance of the westward propagating mode with zonal wave number 2 (SW2), with secondary contributions by westward propagating modes with zonal wave numbers 3 (SW3) and 4 (SW4). Eastward propagating waves are largely absent from the tidal spectrum. Further study will be required for the relative importance of ionospheric conductivities and nonmigrating lunar tides.
Y1  - 2017
U6  - https://doi.org/10.1002/2017JA024601
SN  - 2169-9380
SN  - 2169-9402
VL  - 122
SP  - 12445
EP  - 12463
PB  - American Geophysical Union
CY  - Washington
ER  -