Articles | Volume 33, issue 8
Regular paper 11 Aug 2015
Regular paper | 11 Aug 2015
Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT
H. Y. Fu et al.
No articles found.
Alireza Mahmoudian, Mike J. Kosch, Wayne A. Scales, Michael T. Rietveld, and Henry Pinedo
Ann. Geophys. Discuss.,
Revised manuscript under review for ANGEOShort summary
The polar mesospheric summer echoes (PMSE) are very strong radar echoes observed in the frequency range of 2 MHz up to 1 GHz. Such radar echoes are attributed to the ice clouds formed in the mesosphere and are widely believed to link to global climate change. PMSEs are coherent echoes produced by plasma density fluctuations at half the radar wavelengts. This paper investigates the unresolved problem of short durability of plasma fluctuations at smaller wavelengths in upper atmospheric physics.
Michael T. Rietveld and Andrew Senior
Ann. Geophys., 38, 1101–1113,Short summary
We provide an explanation for mysterious radar echoes that look like increases in electron density during incoherent scatter radar measurements made when a high-power high-frequency (4–8 MHz) radio wave is transmitted up into the ionosphere. These echoes are seen at heights from about 200 to 650 km. We suggest that radar echoes at 930 MHz are guided along the earth's magnetic field by electron density irregularities created by the powerful radio wave, similar to light in an optical fibre.
Thomas B. Leyser, Björn Gustavsson, Theresa Rexer, and Michael T. Rietveld
Ann. Geophys., 38, 297–307,Short summary
Powerful radio waves transmitted into the ionosphere give the strongest turbulence effects in geomagnetic zenith, antiparallel to the magnetic field in the Northern Hemisphere. Our results obtained with the EISCAT (European Incoherent SCATter association) Heating facility in Norway and the EISCAT UHF incoherent scatter radar together with modelling suggest that the pump wave propagates in the L mode, rather than in the O mode that is usually assumed to be involved in such experiments.
Ying Zou, Brian M. Walsh, Yukitoshi Nishimura, Vassilis Angelopoulos, J. Michael Ruohoniemi, Kathryn A. McWilliams, and Nozomu Nishitani
Ann. Geophys., 37, 215–234,Short summary
Magnetopause reconnection is a process whereby the Sun explosively transfers energy to the Earth. Whether the process is spatially patchy or spatially continuous and extended has been under long debate. We use space–ground coordination to overcome the limitations of previous studies and reliably interpret spatial extent. Our result strongly indicates that both patchy and extended reconnection is possible and, interestingly, that extended reconnection grows from a localized patch via spreading.
Jun Wu, Jian Wu, Michael T. Rietveld, Ingemar Haggstrom, Haisheng Zhao, Tong Xu, and Zhengwen Xu
Ann. Geophys. Discuss.,
Manuscript not accepted for further review
David A. Newnham, Mark A. Clilverd, Michael Kosch, Annika Seppälä, and Pekka T. Verronen
Atmos. Meas. Tech., 12, 1375–1392,Short summary
A simulation study has been carried out to investigate the potential for observing ozone and hydroxyl radical abundances in the mesosphere and lower thermosphere using ground-based passive microwave radiometry. In the polar middle atmosphere these chemical species respond strongly to geomagnetic activity associated with space weather. The results show that measuring diurnal variations in ozone and hydroxyl from high-latitude Northern Hemisphere and Antarctic locations would be possible.
Thomas B. Leyser, H. Gordon James, Björn Gustavsson, and Michael T. Rietveld
Ann. Geophys., 36, 243–251,Short summary
Transmission of powerful radio waves into the overhead ionosphere is used to study plasma turbulence processes. It is well known that the ionospheric response to radio waves is the strongest in the direction of the geomagnetic field. We have found evidence that the transmitted radio wave can propagate in a mode that enables the wave to propagate much higher in altitude and deeper into the ionosphere than what is usually expected, which may account for the strong plasma response observed.
O. Havnes, H. Pinedo, C. La Hoz, A. Senior, T. W. Hartquist, M. T. Rietveld, and M. J. Kosch
Ann. Geophys., 33, 737–747,Short summary
Noctilucent clouds were observed by two radars at different wavelengths. Artificial electron heating was applied. As predicted by modelling, there is a general difference between the observations by the two radars. However, for some heater cycles we observed an exceptionally strong, rapid and similar increase in backscatter for both radars when the heater was on. Models predict a considerable difference in reaction. Our observation indicate that the charging models may not be complete.
P. Prikryl, R. Ghoddousi-Fard, E. G. Thomas, J. M. Ruohoniemi, S. G. Shepherd, P. T. Jayachandran, D. W. Danskin, E. Spanswick, Y. Zhang, Y. Jiao, and Y. T. Morton
Ann. Geophys., 33, 637–656,Short summary
Rapid fluctuations in amplitude and phase of radio waves passing through the ionosphere degrade GPS positional accuracy and can lead to navigational errors, particularly during geomagnetic storms. As a function of magnetic latitude and local time, regions of GPS phase scintillation at high latitudes are identified in the context of coupling between the solar wind and the magnetosphere-ionosphere system, which primarily depends on the interplanetary magnetic field magnitude and orientation.
P. Prikryl, R. Ghoddousi-Fard, L. Spogli, C. N. Mitchell, G. Li, B. Ning, P. J. Cilliers, V. Sreeja, M. Aquino, M. Terkildsen, P. T. Jayachandran, Y. Jiao, Y. T. Morton, J. M. Ruohoniemi, E. G. Thomas, Y. Zhang, A. T. Weatherwax, L. Alfonsi, G. De Franceschi, and V. Romano
Ann. Geophys., 33, 657–670,Short summary
A series of interplanetary coronal mass ejections in the period 7–17 March 2012 caused geomagnetic storms that strongly affected the high-latitude ionosphere in the Northern and Southern Hemisphere. Interhemispheric comparison of GPS phase scintillation reveals commonalities as well as asymmetries, as a consequence of the coupling between the solar wind and magnetosphere. The interhemispheric asymmetries are primarily caused by the dawn-dusk component of the interplanetary magnetic field.
V. Pilipenko, V. Belakhovsky, M. J. Engebretson, A. Kozlovsky, and T. Yeoman
Ann. Geophys., 33, 395–404,Short summary
Irregular broadband pulsations and narrow-band Pc5 waves are found to be a ubiquitous element of ULF activity in the dayside high-latitude region. To identify the ionospheric projections of the cusp, we use the width of return signal of the SuperDARN radar. The spatial structure of broadband Pc5-6 pulsation spectral power has been found to have a localized latitudinal peak, not under the cusp proper as was previously thought, but several degrees southward from the equatorward cusp boundary.
N. M. Schlatter, N. Ivchenko, B. Gustavsson, T. Leyser, and M. Rietveld
Ann. Geophys., 31, 1103–1108,
This paper reports the first experimental observation of stimulated Brillouin scattering near the third electron gyro-harmonic induced by high-frequency, high-power radio waves at EISCAT. The stimulated Brillouin scattering has also been correlated with simultaneous observations of the field-aligned irregularities and electron temperature. The observed stimulated Brillouin scattering becomes enhanced for pumping near electron gyro-harmonics.
This paper reports the first experimental observation of stimulated Brillouin scattering near...