TY  - JOUR
A1  - Arridge, Christopher S.
A1  - Achilleos, N.
A1  - Agarwal, Jessica
A1  - Agnor, C. B.
A1  - Ambrosi, R.
A1  - Andre, N.
A1  - Badman, S. V.
A1  - Baines, K.
A1  - Banfield, D.
A1  - Barthelemy, M.
A1  - Bisi, M. M.
A1  - Blum, J.
A1  - Bocanegra-Bahamon, T.
A1  - Bonfond, B.
A1  - Bracken, C.
A1  - Brandt, P.
A1  - Briand, C.
A1  - Briois, C.
A1  - Brooks, S.
A1  - Castillo-Rogez, J.
A1  - Cavalie, T.
A1  - Christophe, B.
A1  - Coates, Andrew J.
A1  - Collinson, G.
A1  - Cooper, J. F.
A1  - Costa-Sitja, M.
A1  - Courtin, R.
A1  - Daglis, I. A.
A1  - De Pater, Imke
A1  - Desai, M.
A1  - Dirkx, D.
A1  - Dougherty, M. K.
A1  - Ebert, R. W.
A1  - Filacchione, Gianrico
A1  - Fletcher, Leigh N.
A1  - Fortney, J.
A1  - Gerth, I.
A1  - Grassi, D.
A1  - Grodent, D.
A1  - Grün, Eberhard
A1  - Gustin, J.
A1  - Hedman, M.
A1  - Helled, R.
A1  - Henri, P.
A1  - Hess, Sebastien
A1  - Hillier, J. K.
A1  - Hofstadter, M. H.
A1  - Holme, R.
A1  - Horanyi, M.
A1  - Hospodarsky, George B.
A1  - Hsu, S.
A1  - Irwin, P.
A1  - Jackman, C. M.
A1  - Karatekin, O.
A1  - Kempf, Sascha
A1  - Khalisi, E.
A1  - Konstantinidis, K.
A1  - Kruger, H.
A1  - Kurth, William S.
A1  - Labrianidis, C.
A1  - Lainey, V.
A1  - Lamy, L. L.
A1  - Laneuville, Matthieu
A1  - Lucchesi, D.
A1  - Luntzer, A.
A1  - MacArthur, J.
A1  - Maier, A.
A1  - Masters, A.
A1  - McKenna-Lawlor, S.
A1  - Melin, H.
A1  - Milillo, A.
A1  - Moragas-Klostermeyer, Georg
A1  - Morschhauser, Achim
A1  - Moses, J. I.
A1  - Mousis, O.
A1  - Nettelmann, N.
A1  - Neubauer, F. M.
A1  - Nordheim, T.
A1  - Noyelles, B.
A1  - Orton, G. S.
A1  - Owens, Mathew
A1  - Peron, R.
A1  - Plainaki, C.
A1  - Postberg, F.
A1  - Rambaux, N.
A1  - Retherford, K.
A1  - Reynaud, Serge
A1  - Roussos, E.
A1  - Russell, C. T.
A1  - Rymer, Am.
A1  - Sallantin, R.
A1  - Sanchez-Lavega, A.
A1  - Santolik, O.
A1  - Saur, J.
A1  - Sayanagi, Km.
A1  - Schenk, P.
A1  - Schubert, J.
A1  - Sergis, N.
A1  - Sittler, E. C.
A1  - Smith, A.
A1  - Spahn, Frank
A1  - Srama, Ralf
A1  - Stallard, T.
A1  - Sterken, V.
A1  - Sternovsky, Zoltan
A1  - Tiscareno, M.
A1  - Tobie, G.
A1  - Tosi, F.
A1  - Trieloff, M.
A1  - Turrini, D.
A1  - Turtle, E. P.
A1  - Vinatier, S.
A1  - Wilson, R.
A1  - Zarkat, P.
T1  - The science case for an orbital mission to Uranus: Exploring the origins and evolution of ice giant planets
JF  - Planetary and space science
N2  - Giant planets helped to shape the conditions we see in the Solar System today and they account for more than 99% of the mass of the Sun's planetary system. They can be subdivided into the Ice Giants (Uranus and Neptune) and the Gas Giants (Jupiter and Saturn), which differ from each other in a number of fundamental ways. Uranus, in particular is the most challenging to our understanding of planetary formation and evolution, with its large obliquity, low self-luminosity, highly asymmetrical internal field, and puzzling internal structure. Uranus also has a rich planetary system consisting of a system of inner natural satellites and complex ring system, five major natural icy satellites, a system of irregular moons with varied dynamical histories, and a highly asymmetrical magnetosphere. Voyager 2 is the only spacecraft to have explored Uranus, with a flyby in 1986, and no mission is currently planned to this enigmatic system. However, a mission to the uranian system would open a new window on the origin and evolution of the Solar System and would provide crucial information on a wide variety of physicochemical processes in our Solar System. These have clear implications for understanding exoplanetary systems. In this paper we describe the science case for an orbital mission to Uranus with an atmospheric entry probe to sample the composition and atmospheric physics in Uranus' atmosphere. The characteristics of such an orbiter and a strawman scientific payload are described and we discuss the technical challenges for such a mission. This paper is based on a white paper submitted to the European Space Agency's call for science themes for its large-class mission programme in 2013.
KW  - Uranus
KW  - Magnetosphere
KW  - Atmosphere
KW  - Natural satellites
KW  - Rings
KW  - Planetary interior
Y1  - 2014
U6  - https://doi.org/10.1016/j.pss.2014.08.009
SN  - 0032-0633
VL  - 104
SP  - 122
EP  - 140
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Soares, Gabriel
A1  - Yamazaki, Yosuke
A1  - Matzka, Jürgen
A1  - Pinheiro, Katia
A1  - Morschhauser, Achim
A1  - Stolle, Claudia
A1  - Alken, Patrick
T1  - Equatorial counter electrojet longitudinal and seasonal variablity in the American sector
JF  - Journal of geophysical research : Space physics
N2  - The equatorial electrojet occasionally reverses during morning and afternoon hours, leading to periods of westward current in the ionospheric E region that are known as counter electrojet (CEJ) events. We present the first analysis of CEJ climatology and CEJ dependence on solar flux and lunar phase for the Brazilian sector, based on an extensive ground-based data set for the years 2008 to 2017 from the geomagnetic observatory Tatuoca (1.2 degrees S, 48.5 degrees W), and we compare it to the results found for Huancayo (12.0 degrees S, 75.3 degrees W) observatory in the Peruvian sector. We found a predominance of morning CEJ events for both sectors. The afternoon CEJ occurrence rate in the Brazilian sector is twice as high as in the Peruvian sector. The afternoon CEJ occurrence rate strongly depends on season, with maximum rates occurring during the northern-hemisphere summer for the Brazilian sector and during the northern-hemisphere winter for the Peruvian sector. Significant discrepancies between the two sectors are also found for morning CEJ rates during the northern-hemisphere summer. These longitudinal differences are in agreement with a CEJ climatology derived from contemporary Swarm satellite data and can be attributed in part to the well-known longitudinal wave-4 structure in the background equatorial electrojet strength that results from nonmigrating solar tides and stationary planetary waves. Simulations with the Thermosphere-Ionosphere-Electrodynamics General Circulation Model show that the remaining longitudinal variability in CEJ during northern summer can be explained by the effect of migrating tides in the presence of the varying geomagnetic field in the South Atlantic Anomaly.
Y1  - 2018
U6  - https://doi.org/10.1029/2018JA025968
SN  - 2169-9380
SN  - 2169-9402
VL  - 123
IS  - 11
SP  - 9906
EP  - 9920
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Soares, Gabriel Brando
A1  - Yamazaki, Yosuke
A1  - Cnossen, Ingrid
A1  - Matzka, Jürgen
A1  - Pinheiro, Katia J.
A1  - Morschhauser, Achim
A1  - Alken, Patrick
A1  - Stolle, Claudia
T1  - Evolution of the geomagnetic daily variation at Tatuoca, Brazil, From 1957 to 2019
BT  - a transition from Sq to EEJ
JF  - Journal of geophysical research : Space physics
N2  - The magnetic equator in the Brazilian region has moved over 1,100 km northward since 1957, passing the geomagnetic observatory Tatuoca (TTB), in northern Brazil, around 2013. We recovered and processed TTB hourly mean values of the geomagnetic field horizontal (H) component from 1957 until 2019, allowing the investigation of long-term changes in the daily variation due to the influence of secular variation, solar activity, season, and lunar phase. The H day-to-day variability and the occurrence of the counter electrojet at TTB were also investigated. Until the 1990s, ionospheric solar quiet currents dominated the quiet-time daily variation at TTB. After 2000, the magnitude of the daily variation became appreciably greater due to the equatorial electrojet (EEJ) contribution. The H seasonal and day-to-day variability increased as the magnetic equator approached, but their amplitudes normalized to the average daily variation remained at similar levels. Meanwhile, the amplitude of the lunar variation, normalized in the same way, increased from 5% to 12%. Within the EEJ region, the occurrence rate of the morning counter electrojet (MCEJ) increased with proximity to the magnetic equator, while the afternoon counter electrojet (ACEJ) did not. EEJ currents derived from CHAMP and Swarm satellite data revealed that the MCEJ rate varies with magnetic latitude within the EEJ region while the ACEJ rate is largely constant. Simulations with the Thermosphere-Ionosphere-Electrodynamics General Circulation Model based on different geomagnetic main field configurations suggest that long-term changes in the geomagnetic daily variation at TTB can be attributed to the main field secular variation.
Y1  - 2020
U6  - https://doi.org/10.1029/2020JA028109
SN  - 2169-9380
SN  - 2169-9402
VL  - 125
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Matzka, Jürgen
A1  - Stolle, Claudia
A1  - Yamazaki, Yosuke
A1  - Bronkalla, Oliver
A1  - Morschhauser, Achim
T1  - The geomagnetic Kp index and derived indices of geomagnetic activity
JF  - Space weather : the international journal of research and applications
N2  - The geomagnetic Kp index is one of the most extensively used indices of geomagnetic activity, both for scientific and operational purposes. This article reviews the properties of the Kp index and provides a reference for users of the Kp index and associated data products as derived and distributed by the GFZ German Research Centre for Geosciences. The near real-time production of the nowcast Kp index is of particular interest for space weather services and here we describe and evaluate its current setup.
Y1  - 2021
U6  - https://doi.org/10.1029/2020SW002641
SN  - 1542-7390
VL  - 19
IS  - 5
PB  - Wiley
CY  - New York
ER  -