scholarly journals Dayside cosmic noise absorption at the equatorward boundary of auroral oval as observed from Maitri, Antarctica ( L  = 5; CGM 62.45°S, 55.45°E)

2016 ◽  
Vol 121 (4) ◽  
pp. 3198-3211 ◽  
Author(s):  
Jayanta K. Behera ◽  
Ashwini K. Sinha ◽  
Geeta Vichare ◽  
Olga Kozyreva ◽  
Rahul Rawat ◽  
...  
Keyword(s):  
Auroral Oval ◽  
Noise Absorption ◽  
Equatorward Boundary ◽  
Cosmic Noise

scholarly journals Case study of the mesospheric and lower thermospheric effects of solar X-ray flares: coupled ion-neutral modelling and comparison with EISCAT and riometer measurements

2008 ◽  
Vol 26 (8) ◽  
pp. 2311-2321 ◽  
Author(s):  
C.-F. Enell ◽  
P. T. Verronen ◽  
M. J. Beharrell ◽  
J. P. Vierinen ◽  
A. Kero ◽  
...  
Keyword(s):  
Solar Proton ◽  
Spectral Irradiance ◽  
Cluster Ions ◽  
Ion Chemistry ◽  
Density Profiles ◽  
X Ray ◽  
Noise Absorption ◽  
D Region ◽  
Electron Density Profiles ◽  
Cosmic Noise

Abstract. Two case studies of upper mesospheric and lower thermospheric (UMLT) high-latitude effects of solar X-ray flares are presented. Sodankylä Ion-neutral Chemistry Model (SIC) electron density profiles agree with D-region EISCAT and riometer observations, provided that the profiles of the most variable ionisable component, nitric oxide, are adjusted to compensate for NOx production during preceding geomagnetically active periods. For the M6-class flare of 27 April 2006, following a quiet period, the agreement with cosmic noise absorption observed by the Sodankylä riometers was within reasonable limits without adjustment of the [NO] profile. For the major (X17-class) event of 28 October 2003, following high auroral activity and solar proton events, the NO concentration had to be increased up to on the order of 108 cm−3 at the D-region minimum. Thus [NO] can in principle be measured by combining SIC with observations, if the solar spectral irradiance and particle precipitation are adequately known. As the two case events were short and modelled for high latitudes, the resulting neutral chemical changes are insignificant. However, changes in the model ion chemistry occur, including enhancements of water cluster ions.

scholarly journals Correspondence between the ULF wave power spatial distribution and auroral oval boundaries

2016 ◽  
Vol 2 (2) ◽  
pp. 46-65 ◽  
Author(s):  
Ольга Козырева ◽  
Olga Kozyreva ◽  
Вячеслав Пилипенко ◽  
Vyacheslav Pilipenko ◽  
Марк Энгебретсон ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Spectral Power ◽  
Recovery Phase ◽  
Temporal Variations ◽  
Auroral Oval ◽  
Wave Power ◽  
Observational Result ◽  
Equatorward Boundary ◽  
Image Satellite ◽  
Magnetospheric Field

The world-wide spatial distribution of the wave power in the Pc5 band during magnetic storms has been compared with auroral oval boundaries. The poleward and equatorward auroral oval boundaries are estimated using either the British Antarctic Survey database containing IMAGE satellite UV observations of the aurora or the OVATION model based on the DMSP particle data. The “epicenter” of the spectral power of broadband Pc5 fluctuations during the storm growth phase is mapped inside the auroral oval. During the storm recovery phase, the spectral power of narrowband Pc5 waves, both in the dawn and dusk sectors, is mapped inside the auroral oval or around its equatorward boundary. This observational result confirms previously reported effects: the spatial/temporal variations of the Pc5 wave power in the morning/pre-noon sector are closely related to the dynamics of the auroral electrojet and magnetospheric field-aligned currents. At the same time, narrowband Pc5 waves demonstrate typical resonant features in the amplitude-phase latitudinal structure. Thus, the location of the auroral oval or its equatorward boundary is the preferred latitude for magnetospheric field-line Alfven resonator excitation. This effect is not taken into account by modern theories of ULF Pc5 waves, but it could be significant for the development of more adequate models.

scholarly journals Pulsating aurora and cosmic noise absorption associated with growth-phase arcs

2018 ◽  
Vol 36 (1) ◽  
pp. 59-69 ◽  
Author(s):  
Derek McKay ◽  
Noora Partamies ◽  
Juha Vierinen
Keyword(s):  
Growth Phase ◽  
Optical Emission ◽  
Border Region ◽  
Emission Region ◽  
Expansion Phase ◽  
Phase Dynamics ◽  
Noise Absorption ◽  
Initial Stage ◽  
Cosmic Noise

Abstract. The initial stage of a magnetospheric substorm is the growth phase, which typically lasts 1–2 h. During the growth phase, an equatorward moving, east–west extended, optical auroral arc is observed. This is called a growth-phase arc. This work aims to characterize the optical emission and riometer absorption signatures associated with growth-phase arcs of isolated substorms. This is done using simultaneous all-sky camera and imaging riometer observations. The optical and riometric observations allow determination of the location of the precipitation within growth-phase arcs of low- (<10  keV) and high- (> 10 keV) energy electrons, respectively. The observations indicate that growth-phase arcs have the following characteristics: The peak of the cosmic noise absorption (CNA) arc is equatorward of the optical emission arc. This CNA is contained within the region of diffuse aurora on the equatorward side. Optical pulsating aurora are seen in the border region between the diffuse emission region on the equatorward side and the bright growth-phase arc on the poleward side. CNA is detected in the same region. There is no evidence of pulsations in the CNA. Once the equatorward drift starts, it proceeds at constant speed, with uniform separation between the growth-phase arc and CNA of 40±10 km. Optical pulsating aurora are known to be prominent in the post-onset phase of a substorm. The fact that pulsations are also seen in a fairly localized region during the growth phase shows that the substorm expansion-phase dynamics are not required to closely precede the pulsating aurora. Keywords. Ionosphere (auroral ionosphere)

scholarly journals Determination of the altitudinal peak of Cosmic Noise Absorption using a vertical parallax technique

2004 ◽  
Vol 31 (7) ◽  
pp. n/a-n/a ◽  
Author(s):  
M. B. Terkildsen ◽  
B. J. Fraser ◽  
H. Yamagishi
Keyword(s):  
Noise Absorption ◽  
Cosmic Noise

Responses of Different Types of Pulsating Aurora in Cosmic Noise Absorption

2019 ◽  
Vol 46 (11) ◽  
pp. 5717-5724 ◽  
Author(s):  
Bing Yang ◽  
Emma Spanswick ◽  
Jun Liang ◽  
Eric Grono ◽  
Eric Donovan
Keyword(s):  
Noise Absorption ◽  
Different Types ◽  
Cosmic Noise

Auroral Zone Cosmic Noise Absorption Pulsations

Nature ◽  
1967 ◽  
Vol 214 (5095) ◽  
pp. 1321-1322 ◽  
Author(s):  
JOHN REID
Keyword(s):  
Auroral Zone ◽  
Noise Absorption ◽  
Cosmic Noise
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