TY  - JOUR
A1  - Xiong, Chao
A1  - Stolle, Claudia
A1  - Park, Jaeheung
T1  - Climatology of GPS signal loss observed by Swarm satellites
JF  - Annales geophysicae
N2  - By using 3-year global positioning system (GPS) measurements from December 2013 to November 2016, we provide in this study a detailed survey on the climatology of the GPS signal loss of Swarm onboard receivers. Our results show that the GPS signal losses prefer to occur at both low latitudes between +/- 5 and +/- 20 degrees magnetic latitude (MLAT) and high latitudes above 60 degrees MLAT in both hemispheres. These events at all latitudes are observed mainly during equinoxes and December solstice months, while totally absent during June solstice months. At low latitudes the GPS signal losses are caused by the equatorial plasma irregularities shortly after sunset, and at high latitude they are also highly related to the large density gradients associated with ionospheric irregularities. Additionally, the high-latitude events are more often observed in the Southern Hemisphere, occurring mainly at the cusp region and along nightside auroral latitudes. The signal losses mainly happen for those GPS rays with elevation angles less than 20 degrees, and more commonly occur when the line of sight between GPS and Swarm satellites is aligned with the shell structure of plasma irregularities. Our results also confirm that the capability of the Swarm receiver has been improved after the bandwidth of the phase-locked loop (PLL) widened, but the updates cannot radically avoid the interruption in tracking GPS satellites caused by the ionospheric plasma irregularities. Additionally, after the PLL bandwidth increased larger than 0.5 Hz, some unexpected signal losses are observed even at middle latitudes, which are not related to the ionospheric plasma irregularities. Our results suggest that rather than 1.0 Hz, a PLL bandwidth of 0.5 Hz is a more suitable value for the Swarm receiver.
KW  - Ionosphere
KW  - equatorial ionosphere
KW  - ionospheric irregularities
KW  - radio science
KW  - radio wave propagation
Y1  - 2018
U6  - https://doi.org/10.5194/angeo-36-679-2018
SN  - 0992-7689
SN  - 1432-0576
VL  - 36
IS  - 2
SP  - 679
EP  - 693
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Soares, Gabriel
A1  - Yamazaki, Yosuke
A1  - Matzka, Jürgen
A1  - Pinheiro, Katia
A1  - Stolle, Claudia
A1  - Alken, Patrick
A1  - Yoshikawa, Akimasa
A1  - Uozumi, Teiji
A1  - Fujimoto, Akiko
A1  - Kulkarni, Atul
T1  - Longitudinal variability of the equatorial counter electrojet during the solar cycle 24
JF  - Studia geophysica et geodaetica
N2  - Ground and space-based geomagnetic data were used in the investigation of the longitudinal, seasonal and lunar phase dependence of the equatorial counter electrojet (CEJ) occurrence in the Peruvian, Brazilian, African, Indian and Philippine sectors during geomagnetically quiet days from the solar cycle 24 (2008 to 2018). We found that CEJ events occur more frequently during the morning (MCEJ) than in the afternoon (ACEJ). The highest MCEJ and ACEJ occurrence rates were observed for the Brazilian sector. Distinct seasonal dependence was found for each longitudinal sector under investigation. The lunar phase dependence was determined for the first time for the Philippine sector (longitude 125 degrees E), and it was shown to be less pronounced than in the Peruvian, Brazilian and African sectors. We demonstrate that differences in CEJ rates derived from ground-based and satellite data can arise from the longitudinal separation between low-latitude and equatorial stations that are used to determine the signal and its consequent time delay in their sunrise/sunset times at ionospheric heights.
KW  - geomagnetism
KW  - equatorial ionosphere
KW  - geomagnetic observatories
KW  - satellite data
Y1  - 2019
U6  - https://doi.org/10.1007/s11200-018-0286-0
SN  - 0039-3169
SN  - 1573-1626
VL  - 63
IS  - 2
SP  - 304
EP  - 319
PB  - Springer
CY  - New York
ER  -