scholarly journals Multi beam observations of cosmic radio noise using a VHF radar with beam forming by a Butler matrix

2011 ◽  
Vol 9 ◽  
pp. 349-357 ◽  
Author(s):  
T. Renkwitz ◽  
W. Singer ◽  
R. Latteck ◽  
M. Rapp
Keyword(s):  
Middle Atmosphere ◽  
Beam Forming ◽  
Cosmic Radio ◽  
Radio Noise ◽  
Spatiotemporal Resolution ◽  
Vhf Radar ◽  
Butler Matrix ◽  
The North ◽  
Noise Absorption ◽  
Cosmic Noise

Abstract. The Leibniz-Institute of Atmospheric Physics (IAP) in Kühlungsborn started to install a new MST radar on the North-Norwegian island Andøya (69.30° N, 16.04° E) in 2009. The new Middle Atmosphere Alomar Radar System (MAARSY) replaces the previous ALWIN radar which has been successfully operated for more than 10 years. The MAARSY radar provides increased temporal and spatial resolution combined with a flexible sequential point-to-point steering of the radar beam. To increase the spatiotemporal resolution of the observations a 16-port Butler matrix has been built and implemented to the radar. In conjunction with 64 Yagi antennas of the former ALWIN antenna array the Butler matrix simultaneously provides 16 individual beams. The beam forming capability of the Butler matrix arrangement has been verified observing the galactic cosmic radio noise of the supernova remnant Cassiopeia A. Furthermore, this multi beam configuration has been used in passive experiments to estimate the cosmic noise absorption at 53.5 MHz during events of enhanced solar and geomagnetic activity as indicators for enhanced ionization at altitudes below 90 km. These observations are well correlated with simultaneous observations of corresponding beams of the co-located imaging riometer AIRIS (69.14° N, 16.02° E) at 38.2 MHz. In addition, enhanced cosmic noise absorption goes along with enhanced electron densities at altitudes below about 90 km as observed with the co-located Saura MF radar using differential absorption and differential phase measurements.

scholarly journals Sudden Cosmic Noise Absorption at 29 Mc/s

1962 ◽  
Vol 15 (1) ◽  
pp. 20 ◽  
Author(s):  
M Krishnamurthi ◽  
G Sivarama Sastry ◽  
T Seshagiri Rao
Keyword(s):  
Solar Flare ◽  
Radio Emission ◽  
Solar Flares ◽  
Initial Conditions ◽  
Cosmic Radio ◽  
Radio Noise ◽  
Terrestrial Atmosphere ◽  
Noise Absorption ◽  
Cosmic Noise

Cosmic radio noise observations at 29 Mc/s made at Hyderabad, India (17� 26' N., 78� 27' E.), have been compared with solar flare data for the year 1958. For flares of importance 3 or 3�, there is a correlation of 84% with regard to related effects observed in the cosmic noise records. These effects are either enhanced radio emission or SCNA's. Particular study of the 9 SCNA's observed during the year and comparison with results of Bhonsle working at Ahmedabad, India (23� 02' N., 72� 38' E.), reveal that (a) even in the case of intense flares initial conditions in the terrestrial atmosphere govern the production and maintenance of an SCNA, and (b) therefore, at least at frequencies above 25 Mc/s, SCNA's cannot be used for patrolling even intense solar flares.

scholarly journals Horizontally resolved structures of radar backscatter from polar mesospheric layers

2012 ◽  
Vol 10 ◽  
pp. 285-290 ◽  
Author(s):  
R. Latteck ◽  
W. Singer ◽  
M. Rapp ◽  
T. Renkwitz ◽  
G. Stober
Keyword(s):  
Middle Atmosphere ◽  
Beam Steering ◽  
Lower Thermosphere ◽  
The Arctic ◽  
Phased Array Antenna ◽  
Vhf Radar ◽  
The North ◽  
Expansion Stage ◽  
Arctic Atmosphere ◽  
High Flexibility

Abstract. The Leibniz-Institute of Atmospheric Physics in Kühlungsborn, Germany (IAP) installed a new powerful VHF radar on the North-Norwegian island Andøya (69.30° N, 16.04° E) from 2009 to 2011. The new Middle Atmosphere Alomar Radar System (MAARSY) replaces the existing ALWIN radar which has been in continuous operation on Andøya for more than 10 yr. MAARSY is a monostatic radar operated at 53.5 MHz with an active phased array antenna consisting of 433 Yagi antennas each connected to its own transceiver with independent control of frequency, phase and power of the transmitted signal. This arrangement provides a very high flexibility of beam forming and beam steering. It allows classical beam swinging operation as well as experiments with simultaneous multiple beams and the use of modern interferometric applications for improved studies of the Arctic atmosphere from the troposphere up to the lower thermosphere with high spatial-temporal resolution. The installation of the antenna was completed in August 2009. An initial expansion stage of 196 transceiver modules was installed in spring 2010, upgraded to 343 transceiver modules in December 2010 and the installation of the radar was completed in spring 2011. Beside standard observations of tropospheric winds and Polar Mesosphere Summer Echoes, multi-beam experiments using up to 91 beams quasi-simultaneously in the mesosphere have been carried out using the different expansion stages of the system during campaigns in 2010 and 2011. These results provided a first insight into the horizontal variability of Polar Mesosphere Summer and Winter Echoes in an area of about 80 km by 80 km with time resolutions between 3 and 9 min.

scholarly journals Cosmic radio noise absorption events associated with equatorward drifting arcs during a substorm growth phase

2004 ◽  
Vol 22 (5) ◽  
pp. 1675-1686 ◽  
Author(s):  
J. R. T. Jussila ◽  
A. T. Aikio ◽  
S. Shalimov ◽  
S. R. Marple
Keyword(s):  
Electron Temperature ◽  
Electric Fields ◽  
Growth Phase ◽  
Energetic Electron ◽  
Cosmic Radio ◽  
Radio Noise ◽  
Particle Precipitation ◽  
Noise Absorption ◽  
D Region ◽  
E Region

Abstract. Cosmic radio noise absorption (CNA) events associated with equatorward drifting arcs during a substorm growth phase are studied by using simultaneous optical auroral, IRIS imaging riometer and EISCAT incoherent scatter radar measurements. The CNA is generally attributed to energetic particle precipitation in the D-region. However, it has been argued that plasma irregularities or enhanced electron temperature (Te) in the E-region could also produce CNA. Both of the latter mechanisms are related to intense electric fields in the ionosphere. We present two events which occur during a substorm growth phase in the evening MLT sector. In both of the events, an auroral arc is drifting equatorward, together with a region of CNA (auroral absorption bay) located on the equatorward side and outside of the arc. Both of the events are associated with enhanced D-region electron density on the equatorward side of the auroral arc, but in the second event, a region of intense electric field and enhanced electron temperature in the E-region is also located on the equatorward side of the arc. We show that in the studied events neither plasma instabilities nor enhanced Te play a significant role in producing the measured CNA, but the CNA in the vicinity of the equatorward drifting arcs is produced by D-region energetic electron precipitation. Key words. Ionosphere (auroral ionosphere; particle precipitation; electric fields and currents)

scholarly journals Statistical signature of active D-region HF heating in IRIS riometer data from 1994–2004

2007 ◽  
Vol 25 (2) ◽  
pp. 407-415 ◽  
Author(s):  
A. Kero ◽  
C.-F. Enell ◽  
Th. Ulich ◽  
E. Turunen ◽  
M. T. Rietveld ◽  
...  
Keyword(s):  
Present Theory ◽  
Cosmic Radio ◽  
Radio Noise ◽  
3 Dimensional ◽  
Noise Absorption ◽  
D Region ◽  
Order Of Magnitude ◽  
Representative Model ◽  
Vertical Beam ◽  
Hf Heating

Abstract. In this paper we study the effect of artificial HF heating on cosmic radio noise absorption in the D-region ionosphere. The effect has earlier been studied theoretically in idealised cases and without experimental verification. Here we present a 3-dimensional modelling of the effect, taking into account the directivity patterns of the vertical beam of the EISCAT Heater at Tromsø, Norway, and the intersecting beam of the IRIS imaging riometer at Kilpisjärvi, Finland. The heater-induced enhancement of cosmic radio noise absorption at the IRIS frequency (38.2 MHz) is estimated to be between 0.02 dB and 0.05 dB in the most representative model cases. However, a statistical study of IRIS data from a selected set of heating experiments carried out during the years 1994–2004 shows that the median effect is between 0.002 dB and 0.004 dB, i.e. an order of magnitude less than theoretically predicted. This indicates that the actual HF heating effect at D-region altitudes is substantially overestimated by the present theory.

scholarly journals Cosmic radio noise absorption related to structures in auroral luminosity

1997 ◽  
Vol 102 (A4) ◽  
pp. 7439-7447 ◽  
Author(s):  
P. H. Stoker ◽  
M. J. Mathews ◽  
M. W. J. Scourfield
Keyword(s):  
Cosmic Radio ◽  
Radio Noise ◽  
Noise Absorption ◽  
Auroral Luminosity

Studies of Radio-Wave Absorption Features at a Subauroral Latitude

1971 ◽  
Vol 49 (11) ◽  
pp. 1411-1418
Author(s):  
M. A. Abdu ◽  
E. L. Vogan
Keyword(s):  
Radio Wave ◽  
The South ◽  
Wave Absorption ◽  
The North ◽  
Noise Absorption ◽  
Radio Wave Absorption ◽  
Cosmic Noise ◽  
Absorption Features ◽  
Absorption Measurements

Cosmic noise absorption measurements at 30 MHz were made simultaneously on two antennas having different beam widths at London, Ontario(53 °N geomagnetic, L = 3.1), a subauroral zone station. The data show that absorption is caused by regions of ionization which exhibit marked spatial non-uniformity within the antenna beams, and which have horizontal extensions limited more toward the south than toward the north of the station. The measurements also indicate the presence of auroral ionization at all times of the day over London.

scholarly journals MAARSY – the new MST radar on Andøya/Norway

2010 ◽  
Vol 8 ◽  
pp. 219-224 ◽  
Author(s):  
R. Latteck ◽  
W. Singer ◽  
M. Rapp ◽  
T. Renkwitz
Keyword(s):  
Middle Atmosphere ◽  
Beam Steering ◽  
Lower Thermosphere ◽  
The Arctic ◽  
Circular Aperture ◽  
Phased Array Antenna ◽  
Spatiotemporal Resolution ◽  
Vhf Radar ◽  
High Flexibility ◽  
New System

Abstract. The Leibniz-Institute of Atmospheric Physics in Kühlungsborn, Germany (IAP) is installing a new powerful VHF radar on the North-Norwegian island Andøya (69.30° N, 16.04° E) in 2009/2010. The new Middle Atmosphere Alomar Radar System (MAARSY) replaces the existing ALWIN radar which has been operated continuously on Andøya for more than 10 years. The new system is a monostatic radar operated at 53.5 MHz with an active phased array antenna consisting of 433 Yagi antennas. The 3-element Yagi antennas are arranged in an equilateral triangle grid forming a circular aperture of approximately 6300 m2. Each individual antenna is connected to its own transceiver with independent phase control and a scalable output up to 2 kW. This arrangement allows very high flexibility of beam forming and beam steering with a symmetric radar beam of a minimum half power beam width of 3.6°, a maximum directive gain of 33.5 dB and a total transmitted peak power of approximately 800 kW. The IF signals of each 7 transceivers connected to each 7 antennas arranged in a hexagon are combined to 61 receiving channels. Selected channels or combinations of IF signals are sent to a 16-channel data acquisition system with 25 m sampling resolution and 16-bit digitization specified which will be upgraded to 64 channels in the final stage. The high flexibility of the new system allows classical Doppler beam swinging as well as experiments with simultaneously formed multiple beams and the use of modern interferometric applications for improved studies of the Arctic atmosphere from the troposphere up to the lower thermosphere with high spatiotemporal resolution.

scholarly journals The enhancement of cosmic radio noise absorption due to hiss-driven energetic electron precipitation during substorms

2015 ◽  
Vol 120 (7) ◽  
pp. 5393-5407 ◽  
Author(s):  
Haimeng Li ◽  
Zhigang Yuan ◽  
Xiongdong Yu ◽  
Shiyong Huang ◽  
Dedong Wang ◽  
...  
Keyword(s):  
Energetic Electron ◽  
Electron Precipitation ◽  
Cosmic Radio ◽  
Radio Noise ◽  
Noise Absorption

scholarly journals Correlation between cosmic noise absorption and VHF coherent echo intensity

2005 ◽  
Vol 23 (5) ◽  
pp. 1543-1553 ◽  
Author(s):  
R. A. Makarevitch ◽  
F. Honary
Keyword(s):  
Signal To Noise Ratio ◽  
Correlation Coefficients ◽  
Spatial Inhomogeneity ◽  
Mutual Orientation ◽  
Echo Intensity ◽  
Vhf Radar ◽  
Noise Absorption ◽  
Cycle Maximum ◽  
E Region ◽  
Cosmic Noise

Abstract. We present examples and statistical analysis of the events with statistically significant correlation between the cosmic noise absorption (CNA) and the signal-to-noise ratio (SNR) of the VHF coherent echo intensity in the area monitored simultaneously by an imaging riometer and two oblique-sounding coherent VHF radars in Northern Scandinavia. By only considering the observations from the narrow riometer beams comparable (in terms of the intersection with the ionosphere) with the VHF radar cells, we identify ~200 one-hour high correlation periods (HCPs) for 2 years near the solar cycle maximum, 2000–2001. The HCP occurrence is maximized in the afternoon (12:00–17:00 UT, MLT≅UT+3), with the secondary peak near the midnight (21:00–02:00 UT). Relative to the VHF echo occurrence, HCPs occur more frequently from 11:00 to 20:00 UT. The diurnal variation of HCP occurrence is similar to that of the 1-h intervals with the lowest mean absorption A<0.25dB. The HCPs are observed more frequently during the winter months, which, combined with the fact that VHF echoes observed during HCPs exhibit features typical for field-aligned E-region irregularities, makes their association with the polar mesospheric echoes (for which some positive CNA/SNR correlation has been reported in the past) very unlikely. Instead, we attribute the high positive CNA/SNR correlation to the synchronous, to a first approximation, variation of the particle fluxes for two different but close sets of energies. By considering the dependence of the CNA/SNR correlation coefficients for both VHF radars (CA1 and CA2) upon the correlation between SNRs for two radars (C12), we show that both coefficients, CA1 and CA2, and the agreement between them decrease drastically with a C12 decrease, which we interpreted through the progressively increasing role of the spatial inhomogeneity of the processes leading to the enhanced CNA and SNR. In this situation, a similarity between the radio signal collection areas should become important, and we demonstrate that the HCP occurrence and mean correlation coefficient decrease as the riometer beams and radar cells become less comparable in terms of mutual orientation and closeness between the points of maximum sensitivity. Keywords. Ionosphere (Auroral ionosphere; Particle precipitation; Instruments and techniques)

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