Connection between the upper ionospheric region of VLF chorus occurrence and the plasmapause position

1986 ◽  
Vol 30 (4) ◽  
pp. 404-410 ◽  
Author(s):  
František Jiříček ◽  
Pavel Tříska ◽  
O. A. Maltseva ◽  
E. E. Titova ◽  
T. A. Yakhnina ◽  
...  
Keyword(s):  
Ionospheric Region

scholarly journals Ionospheric signatures during a magnetospheric flux rope event

2008 ◽  
Vol 26 (12) ◽  
pp. 3967-3977 ◽  
Author(s):  
L. Juusola ◽  
O. Amm ◽  
H. U. Frey ◽  
K. Kauristie ◽  
R. Nakamura ◽  
...  
Keyword(s):  
Flux Rope ◽  
Recovery Phase ◽  
Expansion Phase ◽  
Northern Fennoscandia ◽  
Ionospheric Region ◽  
Image Satellite ◽  
Imaging Camera ◽  
Flux Ropes ◽  
Field Aligned Current ◽  
Upward Current

Abstract. On 13 August 2002, during a substorm, Cluster encountered two earthward moving flux ropes (FR) in the central magnetotail. The first FR was observed during the expansion phase of the substorm, and the second FR during the recovery phase. In the conjugate ionospheric region in Northern Fennoscandia, the ionospheric equivalent currents were observed by the MIRACLE network and the auroral evolution was monitored by the Wideband Imaging Camera (WIC) on-board the IMAGE satellite. Extending the study of Amm et al. (2006), we examine and compare the possible ionospheric signatures associated with the two FRs. Amm et al. studied the first event in detail and found that the ionospheric footprint of Cluster coincided with a region of downward field-aligned current. They suggested that this region of downward current, together with a trailing region of upward current further southwestward, might correspond to the ends of the FR. Unlike during the first FR, however, we do not see any clear ionospheric features associated with the second one. In the GSM xy-plane, the first flux rope axis was tilted with respect to the y-direction by 29°, while the second flux rope axis was almost aligned in the y-direction, with an angle of 4° only. It is possible that due to the length and orientation of the second FR, any ionospheric signatures were simply mapped outside the region covered by the ground-based instruments. We suggest that the ground signatures of a FR depend on the orientation and the length of the structure.

Diagnostics of the HF-pumped ionospheric region using wide-band radio emission

2007 ◽  
Vol 50 (8) ◽  
pp. 593-610 ◽  
Author(s):  
E. N. Sergeev ◽  
S. M. Grach ◽  
P. V. Kotov ◽  
G. P. Komrakov ◽  
G. N. Boiko ◽  
...  
Keyword(s):  
Radio Emission ◽  
Wide Band ◽  
Ionospheric Region

scholarly journals On lunar tides in the upper atmosphere

1939 ◽  
Vol 171 (945) ◽  
pp. 171-187 ◽  
Keyword(s):  
Great Accuracy ◽  
Local Scale ◽  
Scale Height ◽  
Zenith Distance ◽  
Solar Altitude ◽  
Lunar Tides ◽  
Ionospheric Region ◽  
Actual Height ◽  
Maximum Ionization

Although the earliest radio investigations of the ionosphere consisted of systematic measurements of the equivalent heights of reflexion, the tendency in recent years has been to concentrate on measurements of equivalent height as a function of electric wave frequency, since, from such information, maximum ionization concentrations may be estimated. Thus we may say that, in the early measurements, the relation between equivalent height h' and time t was sought, while, more recently, attention has been chiefly focused on the relation between h' and the frequency f . Now it happens that the determination of the critical penetration frequency f c of any ionospheric region, which proceeds by way of ( h', f ) data, does not demand great accuracy in the determination of h' , so that it is easy to understand why little attention has been given to improving the technique of equivalent height measurements. There are, however, a number of interesting ionospheric problems which may be attacked by way of accurate ( h', t ) determinations. It is, for example, clear from simple theory that the actual height at which any ionospheric region is produced should depend on solar altitude, the region being the lower the higher the sun. The variation of the height with the solar zenith distance X depends, moreover, on the local scale height H , so that the study of the variation of region height with the diurnal and seasonal variations of X permits a comparison with theory, and thus a determination of H .

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